What is Ikkitsuukan?
Ikkitsuukan (pure straight) is a mahjong yaku that requires 123, 456, and 789 sequences in the same suit, worth 2 han. Often called “Ittsuu” for short, it’s a beautiful yaku that runs straight from 1 to 9.
Closed it’s 2 han; with calls it drops to 1 han (kuisagari). It’s relatively easy to understand and aim for as a beginner.
Conditions
| Condition | Details | Example |
|---|---|---|
| Same suit 1-9 | Man, Pin, or Sou | 123456789m |
| Three sequences | 123, 456, 789 | 123m 456m 789m |
| Remaining meld + pair | Anything works | Free choice |
| Different suits NG | Must be same suit | 123m 456p 789s = invalid |
Open vs Closed
| State | Han | Points (non-dealer) |
|---|---|---|
| Closed | 2 han | 2600+ |
| Open | 1 han (kuisagari) | 1300+ |
*Kuisagari = losing 1 han when calling
Example Hands
Basic Form
Hand: 123m 456m 789m 234p 5s5s
Complete: 1-9 in manzu + another meld + pairWith Calls
Chi: 123m (sideways) 456m (sideways)
Hand: 789m 456p EECompatible Yaku
| Yaku | Condition | Total Han |
|---|---|---|
| Pinfu | Closed + good wait | 3 han |
| Tanyao | Middle tiles only | 3 han |
| Iipeikou | Two identical sequences | 3 han |
| Sanshoku | Same sequence in 3 suits | 4 han (3 open) |
| Honitsu | One suit + honors | 5 han (4 open) |
| Chinitsu | One suit only | 8 han (7 open) |
When to Aim for Ittsuu
Starting Hand Assessment
| Starting Hand | Decision | Reason |
|---|---|---|
| 6+ same suit | Aim actively | High chance |
| Balanced 1-9 | Easy to aim | Good distribution |
| Mixed suits | Wait and see | Consider sanshoku |
| Dora in target suit | Prioritize | High score potential |
Calling Decisions
-
Early game calls
- 123 or 789 actively
- Lock them in early
-
Mid-game calls
- Chi 456 immediately
- Prioritize completion
-
Late game calls
- Even 1 han has value
- Prioritize winning
Building Strategy
Typical Flow
Starting hand: 5-6 tiles in one suit
↓
Early: Collect 1-3 and 7-9 range
↓
Mid: Complete or chi 456
↓
Late: Ittsuu complete, tenpaiEfficient Approach
-
Prioritize outer sequences
- Build 123 and 789 first
- 456 can come later
-
Use chi effectively
- Call outer sequences
- Self-draw the 456
-
Stay flexible
- Keep sanshoku in view
- Flush hands possible too
Statistics
Occurrence rates:
- Closed: ~1.5%
- With calls: ~2.0%
- Relatively easy 2-han yaku
Compared to Other 2-han
- Chiitoitsu (~3%)
- Sanshoku (~2%)
- Ikkitsuukan (~2%)
- Toitoi (~1.5%)
- Chanta (~1%)
Common Mistakes
-
Different suits confusion
- 123m 456p 789s is invalid
- Must be same suit
-
Sequence order
- Don’t need 123→456→789 order
- Can be scattered in hand
-
Triplet confusion
- 111, 444, 777 doesn’t work
- Must be sequences
-
Kuisagari calculation
- Open: 2→1 han
- Calculate with other yaku
Historical Background
Name Origin
Meaning of “Ikkitsuukan”:
- “Pass through in one go” from 1 to 9
- Continues without interruption
- Also called “Ittsu Ryuu” (one dragon) in Chinese
Why It’s Popular
-
Understandability
- Easy for beginners
- Visually beautiful
-
Practicality
- Relatively easy to make
- 2-han value
-
Achievement feeling
- Fun gathering 1-9
- Satisfaction on completion
Related Terms
- Shuntsu: Three consecutive tiles
- Kuisagari: Han reduction when calling
- Sanshoku: Compatible yaku
- Chinitsu: Often combines
- Honitsu: Often combines
Summary
Ikkitsuukan (Pure Straight) requires 123, 456, and 789 sequences in one suit for 2 han. Closed is 2 han, open drops to 1 han, but it’s popular as an easy-to-understand yaku. Beginners should remember “same suit 1 through 9” and aim actively when dealt many tiles of one suit. Stay flexible with sanshoku and flush combinations while building your hand.
