What is Iipeikou?
Iipeikou (pure double sequence) is a 1-han yaku that requires two identical sequences in closed hand. For example, having two 123-man sequences. The name means “one cup” (identical pair), referring to the matching sets.
It’s visually beautiful and combines well with Pinfu and Tanyao, making it a practical yaku that appears frequently.
Conditions
| Condition | Description | Notes |
|---|---|---|
| Two identical sequences | Exact same tiles | Like 123m×2 |
| Closed only | No calls allowed | Pon/Chi/open kan NG |
| Only one type | Two types = Ryanpeikou | Different yaku |
Examples
Basic Iipeikou:
223344m 567p 789s 55s
└─┘└─┘ (234m twice)Complex Iipeikou:
112233m 456p 678s 99p
└─┘└─┘ (123m twice)Relationship with Chiitoitsu
Note: The following shape is Chiitoitsu, not Iipeikou:
112233445566p 77sThis looks like 3 Iipeikous but is treated as Chiitoitsu.
How to Spot Iipeikou
Easy Patterns
-
Consecutive pairs
2233 → 234 twice (Iipeikou) 5566 → 567 twice (Iipeikou) -
Next to triplet
1112 → Draw 12 for 123 twice 7778 → Draw 67 for 678 twice -
Proper tile sorting
- Easier to spot when organized
- Identical sequences side by side
How to Build It
| Situation | Approach | Probability |
|---|---|---|
| From consecutive pairs | Wait for outer tiles | High |
| Triplet + adjacent | Aim for sequence | Medium |
| Random completion | Unintentional | Low |
Compatible Yaku
| Yaku | Condition | Total Han |
|---|---|---|
| Pinfu | Meet conditions | 2 han |
| Tanyao | 2-8 tiles only | 2 han |
| Riichi | Declare riichi | 2 han |
| Tsumo | Self-draw win | 2 han |
| Sanshoku | Same sequence in 3 suits | 3 han |
High-Scoring Patterns
Riichi + Pinfu + Iipeikou + Tsumo
- 4 han = guaranteed mangan
- Relatively easy to make
Common Mistakes
-
Calling breaks it
- Must be closed hand
- Chi doesn’t work for Iipeikou
-
Triplets don’t count
- 111m twice is not Iipeikou
- Sequences only
-
No overlap with Chiitoitsu
- 1122334455667 shape
- Treated as Chiitoitsu (not 3× Iipeikou)
-
Different sequences don’t work
- 123m and 456m isn’t Iipeikou
- Must be exactly identical
Strategic Value
Pros:
- Easy to miss (opponents too)
- Great synergy with Pinfu/Tanyao
- Riichi possible (closed hand)
- Beautiful shape
Cons:
- Only 1 han (low value alone)
- Closed only means slower
- Hard to aim for intentionally
- Must distinguish from Ryanpeikou
Tips for Practice
Avoid Missing It
-
Sort tiles properly
- Arrange same sequences together
- Visible at a glance
-
Watch consecutive pairs
- 2233, 5566 shapes
- High Iipeikou potential
-
Re-check when winning
- Prevent overlooking yaku
- Iipeikou often forgotten
Development to Ryanpeikou
- Another identical sequence type
- Upgrades to 3-han yaku
- Quite difficult
Related Terms
- Ryanpeikou: Two pairs of identical sequences
- Shuntsu: Three consecutive tiles
- Pinfu: Often combines
- Menzen: Closed hand state
- Chiitoitsu: Similar-looking yaku
Summary
Iipeikou is a 1-han closed-only yaku requiring two identical sequences. The 223344 shape is easy to spot, but it’s often overlooked in hand. Beginners should learn “two same sequences” and “closed only” basics, then develop the habit of checking consecutive pairs for Iipeikou potential. Combined with Pinfu or Tanyao, it can lead to unexpectedly high scores - a valuable yaku to know.