Virtual Sumo

manual.html--Virtual Sumo documentation
(vsumo.exe v0.7 12/30/1999)
Copyright 1999 Andy Tanis

Improvements and enhancements planned for future versions
Major changes/improvements in new versions
Virtual Sumo Tour:
Background info.


If you want to jump right in that's great--the only thing you really need to know are sumo basics--and you can get by without those too, but you probably won't enjoy the simulation very much... Basically, first you can "Create a New Rikishi", or just start with the one included ("Seigatakaigai"). Then you can start into a tournament.

Note: You can only have 1 rikishi at a time--creating and saving a new one will erase the old one.

Come back and check out this manual if you have questions.

The zip file you downloaded contains 3 files:

Improvements and enhancements in the works (or just under consideration)
For updates and news check in at my website:

Major Changes/Improvements In New Versions








Virtual Sumo is a statistical simulation where each rikishi (wrestler) is the composite of many statistics. Stats fall into 3 different categories:

You (the user) create a rikishi by allocating points into these statistics to shape him (or her!) your own way. You can increase these stats through doing well in tournaments (and they can decrease through poor performance). You can work your way up the banzuke (the rankings) just like in the real sport.


This is where you create your own rikishi that you control. You can reroll your attributes until you are satisfied. None of your attributes can be raised over 10 during creation. How an attribute affects Derived attributes (Power, Balance, and Nokosu) is shown to the right of each attribute.

Choose your Primary and Major skills by clicking the panels. The six skills you don't choose become your Minor skills. You have to choose all your Primary and Major skills before you can save the rikishi.

After you allocate all your beginning points to your stats, click the save button if you want to save the rikishi. Save and you can start his or her career. If you click cancel nothing is saved.

You start your first tournament at the bottom of the rankings ("banzuke") at the tender young age of 21.

You can only have one rikishi at a time. If you already have a rikishi and create and save a new one, the old one will be erased. If you want to create a new one and save the current one, move the "rikishi.r" file into a different directory, because that's the file that will be overwritten.


Shikona: Your sumo name.

Real name:  Hopefully you know that...or can make one up...


Height: In centimeters. Minimum height is 170 cm. (5'7").

The shorter you are, the more agile/weak you are, and if you're really tall, you're less agile but stronger.

Weight: In kilograms. (1 lb = 2.2 kg) Minimum is 75 kgs.

Heavier --> Stronger/less agile.

Lighter --> Weaker/more agile.

I would suggest that you set your height fairly close to what you want it to be long term, because it's easier to put on kilos than it is to sprout up centimeters.

For reference, the tallest/heaviest guy in the top division is Akebono, at 204 cm (6'8 1/4) & 232 kg (512 lb). He tends to fall over sometimes, but if he doesn't--watch out! The lightest guy is Terao, at 185 cm (6' 3/4) & 114 kg (251 lb), who is fast as lightning and has toppled guys twice his weight--but if they get a good hold on him (not easy to do), he's in trouble.

Height/Weight Ratio: Height divided by weight--affects balance. Rikishi who are short and stout (but not too fat) have a lower center of gravity. Eg. Akinoshima is more stable than Akebono.

The following 4 attributes range from 1 to 15:

Strength: strong you are!  Strength affects many things, including power and nokosu.

Agility: How fast you are and how well you move around the dohyo. It has great bearing on your balance.

Stamina: The higher your stamina the longer you can last in the ring.

Dohyo Sense: The better sense a rikishi has about where he always is in the dohyo, the harder it is to push him out. It has great bearing on your nokosu.


Derived attributes are based on your attributes.

Power: How much force you execute your strategies with.

Balance: How well you can stay on your feet.

Nokosu: How well you can stay within the dohyo.


Skills are made up of all the moves and strategies rikishi use.

Skill levels range from 1 to 15.

Every rikishi specializes in or is naturally better at certain moves. Each rikishi has 2 primary, 4 major, and 6 minor skills. For user rikishi, primaries start at 8, majors at 4, and minors at 2. The higher priority and the lower the level of a skill, the easier it is to increase (specifics are found in the Chanko Table).

As you win matches and do well in tournaments your potential increases, which allows you to increase your rikishi's statistics. Check the Potential Table for specifics.

SKILL DESCRIPTION Dominates Vulnerable Damage
Yotsu Getting a grip on the mawashi (belt). This strategy usually used by more skilled rikishi. Good for offense and defense, it's less risky than oshi, if you can get a grip. Inashi
Inashi Slipping to the side of the opponent. Hatakikomi
Nokosu Causes a slight loss of balance
Hatakikomi "Slap down" If your opponent seems too far forward and off balance, often he can be pulled forward and helped onto all fours. A risky strategy, because if your opponent regains balance you will have given him momentum against you; and you often kill your own forward momentum. Tsuppari
Balance Causes slight loss of nokosu
Tsuppari "Slapping"  Similar to oshi, but including faster open-handed slaps to the face and neck. A useful technique for keeping the opponent at bay (especially a yotsu expert). Oshi
Oshi "Push"  A basic strategy of pushing your opponent back. Used by many rikishi, it has good potential for "damage", but a bit risky as it can put you off balance. Defense
Nokosu Gain some nokosu back
Defense Overall how tough you are to shove out of or onto the ring. Gake
Balance Gain some balance back
Gake Leg trip. Nage
Nage "Throw" The technique of getting a grip on your opponent (either his mawashi or around his body) and flipping him over. A difficult but potentially devastating move that is often set up with yotsu technique. Yotsu
Tachiai Initial charge of a rikishi and the resulting meeting with the other wrestler -- how fast and with how much power/balance you come out of the blocks with. Your basic proficiency at tachiai.
Jump One of two main types of tachiai. Jumpers like to get out of the blocks quickly and try to overwhelm their opponent, usually with tsuppari or oshi. Harite Henka Nokosu  
Defend The other main type of tachiai. Defenders take their time, keeping an eye out for any tricks. They receive (and try to dissipate) the initial charge of their opponent, then often go for a mawashi grip. Henka Harite Balance  
Henka ("Change") A special instance of hatakikomi is performed at the tachiai and is called "henka." Instead of meeting your opponent straight on you jump to the side, hoping he doesn't notice and sails right by you, putting him off balance and facing away from you--then it's a simple push and he's out of the ring. If he does notice you jumping to the side and corrects his trajectory, you're in trouble. Henka is frowned upon by some, but rikishi still get away with an easy win from time to time. Jump Defend Balance  
Harite Coming into your opponent with a slap to the face at tachiai. Defend Jump Balance  


The banzuke is the ranking of the top division (40 rikishi). Ranks change after each basho (tournament). Generally, have a winning record (8 or more wins--"kachi-koshi"), and you move up the rankings. Have a losing record (8 or more losses--"make-koshi"), and you move down.

The banzuke is broken up into a few subclasses:

Promotion and demotion in Virtual Sumo works pretty much the same way it does in the real thing:

While in the banzuke screen, clicking on a rikishi will bring up their detailed stats.

Rikishi win/loss records are updated after every tournament day. The banzuke is updated at the end of every tournament, after rikishi are sorted according to their records.

The banzuke you start with is based on the November 1999 Kyushu basho. The only differences result from your rikishi being stuck in at the bottom.


This shows detailed statistics and records for each rikishi. You can scroll through them in order of rank. It's a good way to check out the competition, identify strengths and weaknesses, and see how everyone is doing long term.


This plays through a day of action. Matches between computer-controlled rikishi are calculated automatically and the results are displayed. Hit the "Fight" button to start your match. Hit the "Stats" button to first check out your opponents statistics before you fight so you can better formulate a strategy. When your match comes up you get to call your strategies, and see how you and your opponent are doing blow by blow.

The torikumi schedule (who fights who each day) is determined every day just before the matches begin. As a general guideline, Komusubi fight Yokozuna the first couple days, Maegashira with 2 or fewer losses the last 3 days are brought up against sanyaku for a spanking, Yokozuna usually face each other over the last couple days, etc. The algorithms aren't perfect yet (occasionally Yokozuna fight each other too early in the tournament, rikishi face each other more than once in a tournament sometimes, etc.), but it's more realistic than the old hard-coded torikumi schedule, and I plan to tweak it a bit more.

User matches are divided into rounds of 1-3 seconds each, and in each you pick your strategy/technique to use. The Balance and Nokosu ("staying in the dohyo") bars show how each rikishi is doing. Rikishi balance and nokosu levels slowly go down as the match goes on, depending on stamina. With poor stamina you'd better overpower the opponent quickly or you'll be out of energy and either kissing the dirt or flung into the 2nd row seats by your genki-er opponent.

Whoever has a stronger strategy/move depletes either balance or nokosu from the other. Which is drained depends on the type of strategy (eg. Oshi drains nokosu, hatakikomi drains balance, etc. See the Skills table for details on the type of "damage" each move causes.) The power/success of each move is determined by the related statistics and a little luck.

Strategy bonus points are awarded when a rikishi chooses a move that works well against the opponents move. Eg. I choose defense, you choose hatakikomi--I get some bonus points because (usually) trying hatakikomi against a rikishi in a solid defensive position backfires. Somewhat like "Rock, paper, scissors", every move dominates two other moves (one greatly and one moderately), but is itself dominated by two other moves. The Skills table lists what each move dominates and is vulnerable to. What beats what is easy to remember because the strategy buttons are arranged clockwise so that each button beats the two after it (again, it greatly dominates the one right after it, and less so the strategy two after it). Also, a strategy is shown with a larger font if it is a dominating move.

One strategy hint: It's risky being a one-dimensional rikishi. For one thing, the gaming matrix stresses countering an opponents moves, which is hard to do very often if you're a one-trick-pony. Also, computer rikishi aren't stupid--they can catch on to your strategies and counter them with devastating results.

Of course, if a one-dimensional rikishi's one dimension is good enough he may still dominate many opponents. For example, Dejima's strategy is oshi, oshi, oshi (with an occasional hatakikomi throw in)...but he often only needs to push for 2 seconds until his poor opponent is in the 2nd row. But against a more skilled rikishi who can often stop Dejima's initial charge (eg. Takanohana), Dejima's lack of other skills leaves him pretty helpless. Moral of the story: either be real good at one technique and hope no one figures you out, or develop a well-rounded rikishi.

Once a rikishi's balance or nokosu level drops below 1, he loses, although when someone's back is against the wall, they have a slight chance of getting a second-wind (regaining their footing or reversing their position).

Also, as in real sumo, there are 5 shimpan (judges) sitting attentively around the dohyo, and if the match was close, or if they think the gyoji (referee) made the wrong decision, they may hold a mono-ii (meeting). They talk it over, and either decide: 1) the gyoji was correct, and uphold his decision; 2) the gyoji must have had too much sake before coming to work that morning, and reverse his decision; or 3) it was too close to call, and declare a tori-naoshi (rematch).

If you upset a much higher ranked, more skillful, or more gifted rikishi (7 spots on the banzuke, 5 skill points, or 10 total attribute points respectively), your potential increases. After the conclusion of each tournament, you get bonus points if you did well, receiving progressively less for similar records the higher ranked you are. The following tables break down potential increases.


Win-Loss Record
# of Wins 7 8 9 10 11 12 13 14 15
Maegashira 1 2 3 4 5 6 7 8 9
Komusubi - 1 2 3 4 5 6 7 8
Sekiwake - - 1 2 3 4 5 6 7
Ozeki - - - 1 2 3 4 5 6
Yokozuna - - - - 1 2 3 4 5

Differential between you and your opponent
Overall Attributes 5-9 10-14 15-19 20-24 25-29
Overall Skill 8-15 16-23 24-31 32-39 40-47
Banzuke Spot 6-11 12-17 18-23 24-29 30-35
Potential Gained 1 2 3 4 5

At the end of every tournament you get to cash in your potential points during "Chanko" time (chanko is the staple food of all rikishi). You can increase your attributes and skills. You are also allowed to save up your potential points to use at a later "Chanko" session. The table below shows the number of chanko points needed for increases.

(points needed for increases)

Height 170 172 174 176 178 180 182 184 186 188 190-199 200-209 210-219
Points  1 2 3 4 5 6 7 8 9 10 11-20 21-30 31-40

Weight <120 120s 130s 140s 150s 160s 170s 180s 190s 200s 210s 220s 230s 240s
Points 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Current Level Primary Skills Major Skills Minor/Attributes
1-4 1 2 3
5-9 2 4 6
10-14 3 6 9

Computer rikishi also have potential points that they have a chance to cash in (1 per basho) after each basho as well. The younger they are, the higher the chance of fulfilling their potential points. Younger, more promising rikishi (eg. Chiyotaikai, Tochiazuma) start out with more potential points than older rikishi (eg. Akebono, Terao). Computer rikishi weight fluctuates between -3 and + 3 kilos between each basho.

Age is kept track of, and those rikishi over the hill (30+) have a chance of losing a point in a statistic after every basho (the older they are, the higher the chance of "showing their age").

Every basho is 15 days. A tournament leaderboard is displayed from day 8 on. At the end of 15 days, the rikishi with the most wins is declared the Yusho winner (champion). The runnerup(s) are declared Jun-Yusho (runnerup) winner(s).

In the case of a tie after 15 days, there is a playoff (kettei-sen). If only 2 rikishi are involved, it is a simple sudden-death match. With 4 rikishi, there are two rounds, with the winners of the first round taking on each other for the championship. With 6 rikishi, there is an initial round with 3 pairs who fight each other paring it down to 3 rikishi (same with 5 rikishi, with one rikishi getting a bye). With 3, 2 rikishi start, with the winner moving on to face the next rikishi. The first rikishi to defeat the other two competitors in a row is the Yusho winner.

If you find yourself losing pretty badly at first, here are 4 bits of advice:

1) Hey, you're a young guy or gal just breaking into the top division--you'll (hopefully) improve. Even if you have a losing record your first couple tournaments, as long a you accumulate some potential points (and spend them wisely), stick it out for at least a couple more basho.

2) Be more thoughtful about choosing your strategies, and try to anticipate your opponent's moves. Get to know your opponents and their strategies (Dejima favors oshi; Asanowaka favors hatakikomi; etc.).

3) Try creating a new rikishi with different stats--your Derived Attributes are very important. Pay careful attention to how they are affected by your attributes.

(Why Sumo?!)

Well, I became interested in sumo in the spring of 1998 after moving to Japan about 6 months earlier. The first 6 months I saw an occasional fight, and thought what probably 95% (at least of foreigners) of people think about sumo--"Heh, fat guys in diapers pushing each other--interesting (o.k., a bit *bizarre*) but nothing to really grab me..."

Then, over the next couple tournaments, I progressively watched more and more, started to recognize a few more fighters and their distinctive styles and quirks, read a book about sumo and got an understanding about the rules, the ceremonies, the history, etc.

Before I knew it--*BOOM*--I was hooked. I think that once you understand what's going on inside that small dirt ring, and (very important) become familiar with the wrestlers themselves, it's pretty hard not to get hooked! When I'm watching the top division of sumo (the top 40 wrestlers) fight, I'm passionately involved because it feels like they are my 40 brothers--you come to care about (and despise some of) these guys (at least addicts like me do)!

Why a computer simulation?

Two reasons:

1) I love computers, and I've been learning C and C++ (programming languages) for the past year, and hope to keep improving and get some kind of programming job after I leave Japan. This is my first big programming project.  It's actually my first programming project at all--I started while learning C the summer of '98, and I've been working on it (on and off) ever since.

2) As far as I know, there aren't any real sumo simulations out there--I know there are a few for consoles, but from what I've heard, they focus more on arcade action than on strategy and statistics, which is what I want to concentrate on.  There may not be a huge market for a sumo simulation, but whatever market there is seems relatively untapped. And anyway, sumo addicts like myself could never have enough sumo games!


Thanks to the Sumo Mailing List, one of the greatest groups around, for all the sumo insights, games, endless henka debates, and all the rest--but most of all for assuring me that I'm not the only one crazy for sumo!

Special thanks to my wife Cynthia for advice/proofreading/etc. and also (more painfully) putting up with me programming or otherwise thinking about this thing 15 hours a day and coming to bed around 4 am more often than not! (Of course you're my number one priority!) :)

Extra special thanks to our new baby girl, Asia Asami, who puts up with me holding a bottle in her mouth with one hand, and typing with the other.

And remember, "Always do your own brand of sumo!"

December 30, 1999
Andy Tanis