Menzenchin

For the yaku, see menzen tsumo.

A hand is menzenchin 「門前清」, menzen 「門前」 for short, or "closed" in English, when it has not called on another player's discarded tile. This means the player has not called chii, pon, or an open kan. A closed kan (kan when drawing all 4 tiles yourself) does not break the closed state.

A hand that is not closed is known as an open hand. This would be a hand that has called chii, pon, or an open kan. When the hand is open, it cannot score some yaku, and other yaku are reduced in value. While an open hand is usually less valuable than a closed one, it has the ability to use chii and pon to complete faster.

Rule Overview

While a hand is closed:

• It does not have the penalties for having an open hand.
• When winning by ron, the hand gains +10 fu, known as menzen kafu.

While a hand is open:

• Some yaku are invalidated; other yaku are reduced in value. (See the Yaku section below for details.)
• If a hand would score 20 fu, it gains +2 fu, which rounds the hand up to 30 fu.

Yaku

Main article: List of yaku

Closed Only

These yaku can only be scored closed; they cannot be scored at all with an open hand.

1 han		2 han	3 han
Riichi	Iipeikou	Double riichi	Ryanpeikou
Ippatsu	Pinfu	Chiitoitsu
Menzen tsumo

Kuisagari

Kuisagari 「喰い下がり」 is a property of some yaku to lose value when called open. Each yaku affected by kuisagari loses 1 han in an open hand.

From 2 han to 1 han	From 3 han to 2 han	From 6 han to 5 han
Sanshoku	Honitsu	Chinitsu
Ittsu	Junchan
Chanta

Open

These yaku are unaffected by the hand's open/closed status.

1 han		2 han
Tanyao*	Haitei	Sanankou	Shousangen
Yakuhai	Houtei	Sanshoku doukou	Toitoi
Chankan	Rinshan	Sankantsu

* Assuming kuitan (open tanyao) is enabled.

In addition, any yakuman that can be scored open do not lose value if opened.

Closed/Open Tile Groups

Main articles: Mentsu and Naki

A tile group is considered open if it was completed by chii, pon, open kan, or ron. This is distinct from the hand being closed, as hands are not opened by ron (the hand only opens after chii/pon/open kan).

This distinction is important for two reasons:

• Two yaku (and only two yaku) care about closed tile groups: sanankou and suuankou. Every other yaku only checks if the hand is closed. For example, it is possible to score iipeikou with a hand won by ron, even if the iipeikou was completed by the ronned tile.
• Closed triplets and closed kans are worth more fu than their open counterparts. (Sequences are unaffected.)

Strategy

Main article: Naki strategy

The decision on whether to play open or stay closed on the hand will depend on many factors, including your current hand (value/speed), the current round #, and point standings.

Most importantly, every hand requires at least one yaku to win. Any closed hand can declare riichi for a guaranteed yaku, but an open hand requires at least one other yaku. Therefore, when opening your hand, make sure to plan at least one yaku. The most common open yaku are tanyao (if allowed) and yakuhai. though others can be viable too.

For more details, see naki strategy.