​Mahjong Stars

In this lesson, we will cover the concept of defending in riichi mahjong.

 

As mentioned in the previous lesson, the most effective way to defend is to discard genbutsu. However, there are a few other ways to discern tiles that are relatively safe.

 

The most common way is to identify “suji”. Suji is the concept of tiles being in intervals of 3. For instance, 1-4-7man are all along the same suji. This is useful for determining tiles that are safe against ryanmen waits. A ryanmen is the strongest type of basic wait, so using the concept of suji to defend against ryanmen waits is a fundamental aspect of defense.

 

As an example, if an opponent has discarded a 6sou, then 3sou and 9sou would be safe against them, assuming they have a ryanmen wait. The idea is that if they have a ryanmen wait, then it would be furiten if they were waiting on the 3sou or 9sou because they discarded a 6sou earlier. However, this only works against ryanmen waits. They may have a 12sou penchan or 24sou kanchan waiting on the 3sou, or a shanpon or tanki wait on the 9sou. Using suji to defend can be effective, but it is not as safe as just discarding genbutsu.

 

Another way to discern safe tiles is the concept of “kabe”. Kabe literally translates to “wall”, and it is the idea of there being a wall of tiles that make it hard to win on tiles behind that wall. For example, if you can see all 4 of the 7pin, whether they are all discarded, used up in other players calls, used up in your own hand, or some combination of these, it makes it difficult for an opponent to be waiting on the 8pin or 9pin. They may still have a shanpon or tanki wait on these tiles, but that means this concept becomes more effective if you can also see some of the tiles behind the kabe. Therefore, if you can also see 2 or 3 of the 9pin, it makes it much less likely that they are waiting on it.

 

The last thing you can look for are tiles that cannot possibly be used by another player. This can be an extension of the concept of kabe, but it can also apply to honor tiles. For example, the fourth copy of an honor tile is safe against any hand except kokushi musou. If you can already see 4 of any 1 terminal or honor tile, then that fourth copy of another honor tile is 100% safe against everyone.

 

Now that we have covered some basic ways to defend, we need to discuss when to defend. After all, it is pointless to defend against the other players’ hands if none of them are tenpai. Therefore, you mainly start defending once you think another player is tenpai. The easiest way to know is if they declare riichi. You know that a player who declares riichi is tenpai, so that is a good signal to start defending against them.

 

However, it becomes a little bit more tricky if an opponent has an open hand. With that, you have to judge how likely they are to be tenpai based on how many times they have called and how many turns have passed. In general, you should assume that a player with an open hand is tenpai if they have made 3 calls by the end of the first row, 2 calls by the end of the second row, or 1 call in the third row.

 

These “rows” refer to the rows of discards that each player makes. In an average hand, players will discard 17-18 tiles, forming 3 rows of discards 6 tiles long. The idea is that if a player made 3 calls very quickly (by the end of the first row), they are probably already tenpai, or if they made 1 call late in the game (in the third row), they probably made that call to get to tenpai.

 

Lastly, before you defend, you need to decide if it is worth defending. This usually happens on a case-by-case basis. If your hand is already tenpai when an opponent declares riichi, you may choose not to defend to try and win your hand instead. If you think that your opponents’ hands are not very expensive for whatever reason (the most common one being that you can see most or all of the dora tiles), then you may decide to push forward on the basis that dealing in would not cost very many points.

 

However, if your hand is not yet tenpai, does not have a good wait, or would not worth much even if you do win, you should probably just defend. In these cases, it is usually best to “fold”. Folding means giving up any chance of winning your hand and discarding only the safest tiles possible, even if it means breaking up completed sets in your hand. When you fold, you minimize your risk of dealing another player’s winning tile with the expectation that you will only lose points if someone else wins by tsumo or if the hand goes to ryuukyoku. In the latter case, you will only have to pay between 1000 and 3000 points for the tenpai payments.

 

Here is a video by Light Grunty explaining the concept of defense in riichi mahjong: