# Ittsu — Riichi Mahjong Glossary

> Pure straight - a 2-han (closed) or 1-han (open) yaku where you have 123, 456, and 789 of the same suit.

**Source:** https://www.mahjongmaster.co/learn/riichi/glossary/ittsu/
**Author:** Kenji Tanaka (https://www.mahjongmaster.co/about/kenji-tanaka/)
**Publisher:** Mahjong Master (https://www.mahjongmaster.co)
**Published:** 2026-02-18
**Updated:** 2026-03-10
**Japanese:** 一気通貫
**Category:** hand-structure
**Variant:** riichi

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## Ittsu

**Ittsu** (一気通貫, いっつう) is a yaku worth 2 han (closed) or 1-han (open) where you have three consecutive sequences of 1-2-3, 4-5-6, and 7-8-9 in the same suit. The full name translates to "straight through," representing a complete run from 1 to 9. Often abbreviated from "ikki tsuukan."

## How Ittsu works

### Requirements

To achieve ittsu, you need:
- **Three sequences**: 1-2-3, 4-5-6, and 7-8-9
- **Same suit**: All three sequences must be in the same suit (all bamboo, all characters, or all dots)
- **Exact sequences**: Must be those specific three, no other combination counts

For example, 1-2-3 bamboo, 4-5-6 bamboo, and 7-8-9 bamboo forms ittsu in bamboo.

### Han Value

**Closed hand**: 2 han
**Open hand**: 1 han

The drop to 1 han when open makes ittsu similar to sanshoku doujun. You can still call melds to speed up completion, but you lose half the value.

### Strategic Considerations

**Single-Suit Focus**: Ittsu requires nine tiles from one suit, making it partially compatible with honitsu (half flush) or chinitsu (pure flush). Your hand will naturally contain many tiles from that suit.

**Tile Requirements**: You need draws to provide all nine specific tiles (1-2-3-4-5-6-7-8-9) from one suit. This is a significant commitment and reduces flexibility compared to building generic sequences.

**Edge Tile Vulnerability**: The 1-2-3 and 7-8-9 sequences are edge sequences, which are typically less flexible than middle sequences. You must specifically draw 1, 2, 3 and 7, 8, 9 rather than accepting a wider range of tiles.

### Combination with Other Yaku

Ittsu pairs well with:
- **Chinitsu** (pure flush): If your entire hand is that one suit, you score ittsu (2 han) + chinitsu (6 han) = 8 han total, a powerful combination worth baiman or more
- **Pinfu** (all sequences): Ittsu uses only sequences, making pinfu compatible
- **Tanyao**: Incompatible because ittsu requires 1 and 9 (terminals), while tanyao forbids them

### Similarity to Sanshoku

Ittsu and sanshoku doujun share structural similarities:
- Both require three specific sequences
- Both are worth 2 han closed, 1 han open
- Both demand early commitment and specific tile draws

The key difference: sanshoku spreads across three suits (more flexible draws but cannot stack with chinitsu), while ittsu concentrates in one suit (less flexible but stacks with chinitsu).

## Seeing Ittsu in play

Your hand develops with sequences in bamboo. You have 1-2-3 bamboo, 4-5-6 bamboo, and are working toward 7-8-9 bamboo. You call chi on 8-bamboo, completing 7-8-9. Your hand now contains the full straight: 1-2-3, 4-5-6, and 7-8-9 bamboo. Because you called chi, your hand scores **ittsu** at 1 han. If you had kept it closed, you would have scored 2 han. If your entire hand is also bamboo-only, you add chinitsu for massive value.

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*This content is from [Mahjong Master](https://www.mahjongmaster.co), a free educational reference for riichi (Japanese) and American (NMJL) mahjong. When citing this page, please link to https://www.mahjongmaster.co/learn/riichi/glossary/ittsu/.*