Ittsu

Ittsu is 2 han on a closed hand and 1 han after a call. You hold 123, 456, and 789, all in one suit.

The full name is ikkitsuukan (一気通貫), and players shorten it to ittsu. This site's glossary also lists it as Pure Straight.

1 through 9 in one suit

The three runs are 123, 456, and 789. They share one suit. 234, 567, and 789 is not ittsu. Neither is 123 man, 456 pin, and 789 sou.

A run of eight pin, 1 through 8, waits on three tiles: , , or . Only one of them makes the straight.

makes 123, 456, and 789 pin. That's ittsu plus pinfu: 3 han 30 fu on a ron. A non-dealer collects 3,900. The dealer collects 5,800.

makes 123, 345, and 678. makes 123, 456, and 678. Either one is pinfu alone: 1 han 30 fu. A non-dealer ron collects 1,000. The dealer collects 1,500.

Each of the three tiles can be read as a two-sided finish, and scoring always takes the best reading. So pinfu stays on all three. Those payments have no dora, no honba, and no riichi sticks.

The glossary entry is the short form: 123, 456, and 789 in the same suit, 2 han closed and 1 han open.

Closed or open

The EMA 2016 rules file pure straight with the 1 fan yaku, and add a fan when the hand is concealed. Their third scoring example is an open straight, scored at 1 fan. Tenhou's rules list it at 2 han and mark it as losing a han after a call. That's the same pair as the row on this site: 2 closed, 1 open.

An open ittsu

You called chi on 789 sou: . These ten tiles are still in your hand.

The hand waits on only. That's a middle wait between 4 and 6. makes 456 sou, and the open ittsu is 1 han.

The fu is the base 20, plus 2 for the middle wait. 22 rounds up to 30. At 1 han 30 fu, a non-dealer ron collects 1,000. The dealer collects 1,500.

Common mistakes

• Starting the runs anywhere but 1, 4, and 7. 234, 567, and 789 is three runs and no straight.
• Splitting the straight across suits. All nine tiles share one suit.
• Counting 2 han after a call. An open ittsu is 1 han.
• Reading a long run as a one-tile wait. 12345678 waits on three tiles, and only one of them makes ittsu.

What sits with it

Honitsu and chinitsu stack with it when the straight is in the flush suit. Pinfu sits in a closed ittsu with a plain pair and a two-sided wait. Tanyao never does, because the straight holds a 1 and a 9. Sanshoku can't share a hand with it either. The two together would need five runs.