Ittsu

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.”

Detailed Explanation

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).

Usage Example

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.

Related Terms

Sanshoku Doujun: Three colored sequences—having the same sequence in all three suits. Similar structure but spread across suits instead of concentrated.

Chinitsu: Pure flush—one suit only. Stacks powerfully with ittsu since ittsu already uses nine tiles from one suit.

Sequence: A run of three consecutive numbered tiles. Ittsu requires three specific sequences.

Pinfu: All sequences yaku. Compatible with ittsu since ittsu uses only sequences.