|Value||1 han (closed only)|
Iipeikou 「一盃口」 is a standard yaku involving two identical sequences. Identical means that both shuntsu must be of the same numbers and suit. This yaku also requires the hand to be closed. A single open call invalidates the yaku, even if the pattern exists within the hand. If this pattern is found twice in one hand, an alternative yaku, ryanpeikou, is scored.
Arrangement of tiles is irrelevant, as long as two groups of tiles form the identical sequences.
This yaku is usually presented as three groups of consecutive pairs. However, the rule interpretation views them as a two sequences. Potential acquisition of this yaku is best recognizable when five out of the six tiles are present in the hand.
Iipeikou requires two sequences, and as a result is incompatible with sanshoku doukou, toitoi, honroutou, chiitoitsu, sanankou, and sankantsu, all of which require either at least three koutsu/kantsu or a seven pair structure. The final incompatibility is with ryanpeikou, as ryanpeikou implies iipeikou and so iipeikou is not counted.
- Iipeikou in Japanese Wikipedia