Riichi Mahjong · Closed 2 / open 2

Sanankou (Three Concealed Triplets) in Riichi Mahjong: Han, Rules and the Shanpon Trap

In riichi mahjong, Sanankou (three concealed triplets) is worth 2 han: your winning hand contains three triplets you completed with your own draws (concealed triplets, ankou). The rest can be sequences or called sets — it stays 2 han even with an open hand.

The rules for Sanankou

• All three triplets must be drawn by you (concealed); a pon makes an open triplet, which doesn't count
• A closed kan (ankan) counts as a concealed triplet; open and added kans don't
• The fourth set can be a sequence or an open triplet, and you may call: still 2 han open
• A triplet completed by ron is open: on a shanpon (two-pair) wait, the set finished with someone else's discard is not concealed

The shanpon trap

Two concealed triplets plus two pairs on a shanpon wait looks like "sanankou whichever tile comes" — but only a tsumo gives it.

Draw the same 6 dots yourself and it's sanankou, tanyao and menzen tsumo together. On a shanpon sanankou wait, tsumo and ron are worlds apart.

How Sanankou is scored

The yaku, han, fu and points below are computed live by the same scoring code the game uses.

Sanankou also brings lots of fu: a concealed triplet of simples is 4 fu, of terminals or honors 8 fu (an open triplet is half). Three of them often push a hand to 40–50 fu, so it scores well for its han.

Common combinations:

How it relates to other yaku

• Toitoi: if all four sets are triplets, toitoi comes too. One pon plus three concealed triplets on a single wait is toitoi + sanankou.
• Suuankou: four concealed triplets is a yakuman. A closed four-triplet shanpon wait is suuankou on tsumo, but only sanankou + toitoi on ron.
• Sankantsu: closed kans count as concealed triplets, so three closed kans give sanankou + sankantsu.
• Sanshoku doukou: the same number as a triplet in all three suits; draw all three yourself and sanankou is added.

Sanankou odds

Three triplets want lots of pairs to start. A 13-tile starting hand has 3 or more pairs about 15% of the time.

In 40,000 hands between four normal-level computers on this site, sanankou appeared in 0.26% of wins, averaging 13,700 points. 79% of those wins were tsumo — only a tsumo keeps a shanpon triplet concealed — far above the 37% tsumo rate across all wins.

Source: 40,000 computer hands on this site (all four at normal level), 33,226 wins. A win usually has several yaku, so the shares add up to more than 100%.

Sanankou in other mahjong styles

• Taiwanese mahjong has "three concealed pungs" too (Taiwanese mahjong tai list); with 16-tile hands there are four and five concealed pungs as well
• Chinese Official (Guobiao): "Three Concealed Pungs", 16 fan (Guobiao fan list)

To try it yourself, open a table of free online riichi mahjong — the computers play with you and count han, fu and points for you.

FAQ

How many han is Sanankou?

Sanankou is 2 han, and still 2 han when open — no kuisagari.

Does a ron on a shanpon wait count as Sanankou?

No. The triplet completed by ron is treated as open; only a tsumo makes it concealed. On a single wait, a ron on the pair leaves all three concealed triplets intact.

Can you call and still get Sanankou?

Yes. As long as three other triplets were drawn by you, a pon or chi elsewhere is fine.

Does a closed kan count as a concealed triplet?

Yes. An ankan counts; open and added kans do not.

Related yaku

Toitoi Closed 2 / open 2 Four triplets and a pair, still 2 han when open. Examples, scoring combos and how many starting pairs you need. Suuankou Yakuman（closed only） Four concealed triplets, closed only — a yakuman. Shanpon needs tsumo, a single wait wins on ron too (double yakuman here), and how many pairs you need. Sankantsu Closed 2 / open 2 Three kans by one player — 2 han, even open. Rules, big fu, common combos and the four-kan draw.