Author: Flowingcloud
Shoutout to the various people in ARML for looking over this initial post and giving me feedback! Please contact Flowingcloud if there are any typos.
Introduction
New year new series!
This is the start of Flowingcloud’s Learning From Pros series where we explore how to improve mahjong play with real examples from pro mahjong matches. The concepts introduced in this series and thought processes introduced in posts are applicable to all levels of mahjong, though this series mainly targets beginner and intermediate players. Hopefully, I will be able to post at least once of these per week.
Today, we will be taking a look at Uotani Yumi pro, who has won the Mahjong Nihon Series 2023 and became the 18th season Jyoryuu Ouka (her 4th time!) last month (December 2023). In the final table, Uotani played phenomenally, winning three out of the four games in the final set against top-class players. One hand that gained a lot of attention online was her hand in East 2 in the first hanchan of the set.
Today’s lesson looks at micro-decisions. It is one thing to learn the concepts, but applying the fundamentals is diffcult. At higher levels, everyone has these pretty nailed down. At that point it comes to the small decisions made along the way that can make or break a hanchan. This first episode emphaizes how almost everyone discard has a meaning, and hopefully provides a broader perspective to how you approach the micro-decisions in your gameplay. The following hand played by Uotani exemplifies how these microdecisions can pay off for you in the end.
Gameplay
Match: https://www.youtube.com/live/sqAUWCOGn4M?si=0TzE3gESOyltAMyC
Ruleset: WRC (aka-nashi; 5/15 uma)
Player: Uotani Yumu
Situation: Uotani starts with a relatively good hand—two dora and an ankou of 3s. Although the hand might be somewhat restrictive with the 1s pair and 1m pair in hand, Uotani wants to try her best to win this hand. She has a kanchan of 4-6m and relatively good floaters (2p and 5p) so the hand is somewhat playable, especially if she is able to pair up the East for an easy yakuhai + dora 2 hand.
turn 1
This is just basic efficiency. Uotani is sitting in the South seat and although 9s was the first tile cut by the dealer, she just wants to play her hand with as much future tile acceptance as possible.
turn 2
Uotani is now especially happy that she has a free path to a 3 han hand with the East paired up. Now, the plan is to call East and go for a quick 3,900/5,200 hand.
turn 3
Initially when I saw the 5p discard live, I thought the more proper play was to discard the 2p. However, after thinking it over afterwards, the 5p actually does make more sense.
The 8m draw gives Uotani a ryankan wait, which while inefficient is still a good shape. That then leaves the floating 2p or 5p tiles as mentioned before. However, she has 4 pairs in hand (the ankou of 3s can easily be turned into a pair) and so if given the opportunity could pivot to chiitoi, dora 2. The 5p discard then sets up the 2p suji trap later should she go down that avenue, and the 2p in general is a better chiitoi tile to wait on.
turn 4
Ironically enough, Uotani draws the 2p trap/chiitoi wait that she had just set up. She is iishanten for chiitoi, dora 2 which if riichi and tsumo are added is the proverbial shortcut to haneman.
However, she has the pair of East in her hand, which means she could easily pivot to something like toitoi, east, dora 2 or 3 for mangan or haneman. She also has the added benefit of her pairs being edge tiles, which are generally more likely to come out. The 4m discard sets up another double suji trap in case she needs the 1m or 7m, but also has the added benefit of (a) being a more edge tile than the central 5m, and (b) more likely that she could pair up the 6m or 8m which would give her to chiitoi tenpai should the opportunity presents itself.
turn 5
I would imagine there would be quite a few Western players out there who would “hit the button” and kan the 3s, thereby ruining your chiitoi iishanten. However, even if she were to go towards toitoi, there is no need to give unnecessary information to the rest of the table that certain tiles are effectively useless (including the 1s dora in this case). Doing so would likely cause the rest of the table to either immediately discard the dora or instead to hoard it to try and use it for their own tricky wait. By keeping the 3s block concealed, her opponents could also consider keeping the 1-2s penchan as a viable wait to force dora usage.
turn 6
This is another point where Uotani shows how great of a player she is by making an excellent decision that allows her the best opportunity to complete this hand.
Like the 2p earlier, she manages to fill in the suji trap wait she was setting up in the 7m. This gets her iishanten for a regular hand, and after a long think, she decides to pivot and forego continuing to hedge chiitoi as an option.
There are several reasons that it is preferable to shift away from chitoi iishanten:
- Although going chiitoi provides the most tile acceptance to tenpai, there are actually less number of tiles to win when the hand achieves tenpai.
- Chiitoi Tanki Wait: max 3 tiles
- Shanpon Wait: max 4 tiles
- The hand’s value caps the hardest when going for a regular hand. First, you’ll have acceptance for another 1s dora draw. Also, if this hand stays closed, then you’ll have sanankou.
- The plan to pon East has never changed. Calling East for tenpai for 3,900/5,200 point win and a potential 8,000 (via 1s dora win) point win.
There are realistically only two options to discard in this scenario since you do not want to cut East pair or dora 1s pair: Cut 1m pair or 2p pair.
In this scenario, what is the main factor that Uotani is considering? Uotani is considering which tile she is more likely to draw, and let’s dig deeper into the thinking process. 1m and 2p are both suji that if I may emphasize, were both suji baits that were DELIBERATELY set up by Uotani. Additionally, both 1m and 2p have not been cut yet, so statistically, the chance that Uotani draws 1m or 2p is exactly the same, right?
No, Uotani employs good wall-reading skills to figure out that 2p is most likely to draw, but why is that? This is due to the 3p tsumogiri followed by the 4p tsumogiri from Takeuchi (sitting West seat) on her right and 4p tedashi from Shiratori (sitting North) across from her. It would be strange for both these tiles to be cut so early if either of them have a 2p in their hands unless they have an ankou (which is not possible since Uotani has two 2p).
Meanwhile, there is close to zero information regarding the 1m at all. Additionally, Shiratori (toimen) has cut a concerning amount of middle tiles from his hand in the first row, indicating that their hand might potentially be a chanta, junchan, or a non-standard hand. Considering that dora is 1s, it would make sense for Shiratori to potentially go for a junchan + dora hand, which means it would not be surprising if they happened to be mochimochi on 1m pair.
In conclusion, Uotani ends up cutting the 1m pair, due to information that two out of three players are unlikely to have 2p, while there is unclear information whether the 1m is being used in all the other three player’s hands.
turn 8
This is a standard swap considering that 1m is a relatively live tile and 6m is genbutsu for Shiratori (toimen). Additionally, 6m temporarily becomes a very strong kutsuki tile, allowing for an easy 2p pair drop to play a ryanmen if 5m or 7m become drawn.
Manzu Development:
Draw 
: 
Draw :
turn 9
Call: Shiratori (toimen) declared chii 
and cut 
.
Yes, this is always a riichi. Just because you see a wall of 3s does not mean other people have that information. Thus, the 1s dora will most likely not come out naturally, and 2p is suji that Uotani had already set up. Additionally, if you tsumo 2p, the hand will be Tsumo, Sanankou, East, Dora 2 for a total 6 han, however, Riichi + Dora (1s tsumo), or Riichi + Ippatsu or Ura will bump the hand up into a baiman tsumo. This is currently East 2 of the first game of the series and raw point gain is important for players to prioritize to create a buffer for later situations and scenarios. Not to mention, with a hand that has good value, you want to declare riichi to apply pressure on other players and make them fold.
Additionally, a noteworthy micro-decision from Uotani to declare riichi on the 6m instead of the 9m, identifying that Shiratori (toimen) might be going potential chanta or junchan, and giving a potential 9m pon to them.
turn 11
Turn 11: Tsumo 2p!
Two turns after the riichi, Uotani successfully wins her hands. Riichi, Tsumo, Sanankou, Dora 2 for an explosive haneman tsumo.
Conclusion
Although Uotani did have an incredible amount of luck in that specific hand, it is important to note that every decision made by Uotani pro had a very specific reasoning and the flexibility that she maintained throughout the entire hand just shows the difference between a regular mahjong player versus a pro mahjong player. If Uotani had just willy-nilly discarded 2p before 5p because it was an outer tile, then none of the following plays would have occurred. Most likely, Uotani would have won a cheap 3,900 point hand instead of a haneman tsumo.
The point that I would like to highlight is the importance of capitalizing on strong, expensive hands and making sure that you are constantly thinking about every discard you make. Additionally, Uotani also showed a prime example of why suji should not be completely trusted against good players, since many players at this caliber of play constantly set up suji traps like what Uotani did in this hand.