Iipeikou 一盃口

Iipeikou is two identical runs in the same suit, in a closed hand. It is worth 1 han, closed only.

Iipeikou is the yaku you often find rather than build. Two copies of the same run in the same suit, a closed hand, and a han appears from nowhere.

Also called: Pure Double Sequence

What It Is

2-3-4 Characters twice: iipeikou, here with pinfu too.

Iipeikou (一盃口, “one cup”) is two identical runs: same numbers, same suit. 2-3-4 Characters and 2-3-4 Characters again counts; 2-3-4 Characters and 2-3-4 Circles doesn’t (that’s heading towards sanshoku).

The rest of the hand can be anything: more runs, triplets, any pair.

What It’s Worth

What it’s worth at each table
Table	Called	Worth
Riichi	Iipeikou	1 han, closed only

One pair of identical runs, or two
Table	Called	Worth
Riichi	Iipeikou	1 han, closed only
Riichi	Ryanpeikou	3 han, closed only

Iipeikou is 1 han, closed only. Two separate pairs of identical runs is ryanpeikou, 3 han, closed only, which replaces iipeikou rather than adding to it.

Closed Or Open

Closed only. Chi one of the two runs and the yaku vanishes, even though the tiles look the same on the table. If you’re one tile from iipeikou, it’s often worth waiting to draw it rather than calling.

That’s the real cost of the yaku: it keeps you closed, and a closed hand is slower. The payoff is that riichi stays available, so iipeikou often arrives as part of a riichi hand worth two or three han before any dora.

How To Build It

Shapes like 3-3-4-4-5 or 2-3-3-4 are your clues. They look clumsy, but they’re one tile from doubling a run. Keep them when the hand is closed and there’s still time.

Iipeikou often turns up alongside pinfu and tanyao, since all three like middle-number runs.

Watch which tile finishes it. 2-2-3-3-4 Characters with a pair elsewhere waits on 1 or 4, and only the 4 makes the second 2-3-4. Both tiles still win; one is just worth more.

A ryanpeikou hand, 2-3-4 twice and 5-6-7 twice plus a pair, is also seven pairs if you look at it the other way. The scorer reads a hand every way it can and keeps the reading worth the most, so you always get the better of ryanpeikou or chiitoitsu, never both.

Common Mistakes

Calling one of the runs. Open is open, even for a chi you’d have drawn anyway.
Counting two different suits. That isn’t iipeikou, though three suits could be sanshoku.
Breaking a pinfu wait to chase it. A good two-sided wait usually beats the extra han.

What It Combines With

Riichi, pinfu, tanyao and menzen tsumo are its natural friends. With a flush it gets big fast: a closed chinitsu often contains an iipeikou without even trying.