Tuesday, 7 February 2012

Defence theory(12): Detailed explanation of each type of melded sets(Part 1)

Source: http://blog.jpmahjong.net/read.php/552.htm

In the previous article, the author mentioned the important signals related to melded sets. This article will introduce in detail each type of melded sets and things to note.

As melded sets will expose information regarding the hand, if used appropriately, it will greatly help in making the proper judgement. Our aim is to use the melded sets to deduce the following.
1. Value of the hand
2. Area of waiting tiles(Or from another perspective, which tiles are safer.)

The following will explain in details the commonly seen types of melded sets.
1. Calling of middle tiles
This can be said to be the most commonly seen melded set in Japanese mahjong. Of course, the melded sets of the opponent are all middle tiles. The largest characteristic about calling middle tiles is that it's difficult to form with other yaku. (Among them, tanyao sanshoku has the highest chance of appearing, but even the chances of getting it is not high.) Hence, the amount of dora in the hand is the determining factor of the hand's value.

So once middle tiles are called, you first need to estimate the whereabouts of the dora. One hand of game has 7 dora(four indicated dora and 3 aka dora). The more dora you can see, the lower the chances that the opponent has a huge amount of dora. Also, if the attacker is really proactive at calling tiles(for example, calling 1 or 2 mentsu very early), then the chances of having a high value hand is higher. Sometimes when we know that there is a high chance that the opponent only have a 1000 or 2000 points hand, we can consider ignoring them.

Against calling of middle tiles, it's easier when it comes to defending, as any yaochuhai is a safe tile. However as the area of waiting tiles is narrow, over reliance on suji-pai and one chance tiles, especially dora soba, can be dangerous.

2. Somete
Like calling of middle tiles, this is also a commonly seen melded set. It's easy to judge if it's a honitsu or chinitsu melded set, as you can see it from your opponent's discards.

Somete has a narrow area of melded set and can be easily recognized, but it's return is usually higher. Somete usually have at least 3900 points, mangan or even haneman are not a rare sight.

For this reason, somete has defence theory like suji-pai etc. Unless it's a genbutsu or tiles incapable of becoming mentsu, or else it's a dangerous tile.

3. Toitoihou
Toitoihou attacks are a common sight in beginners' games, but in higher levels of mahjong games, the chances of appearing is lower. When the opponent often pon tiles, and the discards are made up of random middle tiles, then the chances of toitoihou is large.

The lethality of toitoihou is not low either, it's normally between 2500 to 8000 points. Additional han values are usually from yakuhai 9 out of 10 times. So if you note the yakuhai that have not yet appeared, you can probably estimate the value of the opponent's hand.

As toitoihou is always waiting on tanki or shanpon, there are no suji-pai. Live tiles, no chance tiles and yakuhai are all ultra dangerous. Tenpai is usually on easier waits, therefore middle tiles that have been discarded twice are relatively safer. And when we go into betaori, sometimes we would discard koutsu middle tiles.

4. Yakuhai
Yakuhai tiles are express tickets to winning. You'll get yaku as long as you can pon with it, and as it restricts tile shapes the least, it becomes easier to form hands.

Not only is it easy to combine it with other common yaku(toitoihou, honitsu), a dealer's double ton or yakuhai dora 2/3 are all powerful attacking methods in Japanese mahjong.

As the hand varies greatly, it's harder to deduce the value and waiting tile of the opponent's hand. Normally, the first thing you should do is to note the amount of dora tiles that have not yet appeared, and whether or not the opponent's discards show any characteristics of other yaku.

As for defending, once the signs of being in tenpai appears, treat it as a normal riichi as the waiting tile is not restricted. But as there are melded sets, we can obtain more information regarding what tiles are safe or dangerous:

a) Tiles that have not appeared, are all dangerous tiles. (Translator note: For those of you who can read Chinese, you might notice that I didn't translate this sentence fully. The reason is that it didn't make any sense. The author said that the tile discarded by the attacking player after making the final mentsu is a dangerous tile. Since the attacker cannot ron on a tile he discarded, how can that be a dangerous tile? I will leave it like this until I understand what he really meant.)
b) Tiles discarded by the kamicha of the attacking player but have not been called, are usually safer. The reason is that this proves that that tile is not need by the attacking player. (If it's a menzen, even if others discard a tile you want, you can't call on it.)

(As the current section is too long, the rest of the article will be moved to the next section.)
(To be continued.)


  1. I can't read a word of Chinese, but when the author states that the tile discarded after the final mentsu is dangerous, perhaps he means that tiles connecting to that tile are dangerous? If someone discards a 4P after calling, it may well have come from an incomplete shape like 344 or 445.

    1. I doubt it. That would be something like discard reading which the author seems to detest.

  2. I think I understand what the author was trying to say, and this is something I do a lot of times against an opponent who pon everything. as you have said the opponent who is doing the pon and chi all the times, I tend to target the discard he is making, so I can ron that discard from other player who thinks that tile is safe 100%, my english isn't very good but I hope I made it clear how this thing works, seeing how I do it a lot of times and it is worth it, I even target discarded tiles from the riichi opponent, it is easy way to target the other player.

    and I want to thank you for this blog about mahjong riichi, it is a gem I tell you, thanks.