Riichi is one of the four types of yaku in Japanese mahjong and holds an important position. Starting from today, I will be explaining various judgements related to riichi.
(Discussions related to situation judgements is still work in progress, it's just that collecting examples takes time. They will be posted once they're finished.)
(Translater note: The author is talking about another series of articles related to situation judgements. I decided to translate riichi theory first.)
To understand how to judge riichi, first you need to understand what is riichi. I've mentioned it before previously in articles of a higher difficulty, but this time is for beginners and the theories will be explained in detail. Today will be about the advantages of riichi.
Beginners tend to misunderstand riichi. The most common problem with them is underrating the advantage of riichi. Therefore it's important to understand the benefits of riichi.
1) Increase your hand value
Many people underestimate the attacking power from riichi. People used to say: "Pinfu-nomi's 1 han is only worth 1000 points, while there's only 2000 points after riichi. There's only 2000 points, so you should damaten."
For now, we won't discuss whether pinfu-nomi should declare riichi, but whether or not riichi can increase your original hand's value by 1 time, and pinfu-nomi is not just 1300 points.
I believe everyone has seen these kind of tiles:
Riichi Ippatsu Tsumo Ura-dora 1
Riichi Ura-dora 3
Riichi Ippatsu Tsumo Pinfu Ura-dora 1/2
With riichi, it's not rare to see examples of worthless hands turning into mangan or haneman. Riichi on average will have 1/3 ura-dora, and winning hands with riichi have ippatsu 20% of the time. If you add these up, in fact riichi has a value of 1.5-1.6 han. According to statistics, winning hands with pinfu-nomi riichi has 3000 points and above on average. Riichi has the ability to increase the value of pinfu-nomi by 3 times or more.
In addition, riichi will increase your tsumo proportion. If your hand is 2600 points, and you win on another player's discard while in damaten, the difference between the player who dealt in and the other two players is 5200 and 2600 points respectively. However if you declare riichi, even if you tsumo and didn't have any ura-dora, the difference between you and the other players is 5000 to 6000 points. There's a huge difference.
2) Restrict your opponent's dicards
This is something that is often neglected by most beginners and even some intermediate players.
Once someone declares riichi, unless the others have good tiles, they will not attack recklessly due to Japanese mahjong's payout system. This way, the opponents have lesser chance of winning. On the other hand, once the opponents have lower chances of winning, the amount of chances that you can draw tiles increases, indirectly increasing the value of the winning hand.
This explains why players declare riichi with a suuankou tenpai, the main motive is to increase the chances of drawing tiles.
3) Makes certain tiles easier to wait on
This is a tactic that everyone knows.
Luring the opponent to discard the suji-pai of the riichi tile(especially 19 suji-pai), guest wind, no chance tiles etc, will achieve the desired result.
However I ask everyone not to abuse this tactic, and only use it when it's suitable.
As for riichi's disadvantages, they will be discussed after my new year vacation.