Kanchan
Kanchan 「嵌張」 is a wait pattern that completes with the middle number of a sequence.
| Kanji | 嵌張 |
|---|---|
| English | Closed wait, Middle wait |
| Fu | 2 fu |
| Tile types waiting | 1 sided wait |
| Tiles available | 4 tiles |
| Pattern example |
  |
| Tenhou.net example | Kanchan |
Pattern
Fu
Kanchan is awarded 2 fu upon winning, thus disqualifying the hand from pinfu.
Strategy
Kanchan is considered to be a "bad wait", because it can only wait for a maximum of 4 tiles. Therefore, it is worse for hand development than ryanmen. Like the other bad waits, kanchan can be used to suji trap opponents.
In general, inner kanchans > outer kanchans > penchans when it comes to tile efficiency. See below for details.
Ryankan
A ryankan ("double closed wait") is an extended form of a kanchan, only available before reaching tenpai. A ryankan shape is composed of three tiles that are each 2 apart, such as:
| Pattern |    |
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|---|---|---|---|
| Tiles to complete | |
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A ryankan is effectively the same as having 2 different kanchans; it waits for 8 tiles of two types (4 tiles per type).
However, you cannot enter tenpai with a ryankan. If you would reach tenpai without completing the ryankan, you'd have to discard one of its three tiles, turning it back into a weak kanchan wait.
Example hand with ryankan shape:
With the example hand above, if you drew 
, you would have to discard either or to enter tenpai. You end up with a bad wait, but with one significant advantage - a ryankan always forms a suji trap. Here, if you discarded the 6s, you would wait on the suji 3s, thus making it more likely for others to deal in. This is why a suji of the riichi declaration tile is considered more dangerous.
Inner vs Outer Kanchan
There are two different types of kanchan: inner and outer.
| Type | Tiles | |||
|---|---|---|---|---|
| Inner | |
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| Outer | |
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Inner kanchans are generally superior to outer kanchans because they are easier to upgrade.
- A
kanchan can be upgraded by drawing 
(turning into ) OR 
(turning into ). It can also be turned into a ryankan when drawing either 
or 
.
- A
kanchan can only be upgraded by drawing (turning into ). It can be turned into a ryankan when drawing only.
An inner kanchan can be upgraded by twice the amount of tiles, so inner kanchans are overall stronger. Note that an inner kanchan waits on a middle tile. As middle tiles are harder to win with, an inner kanchan is worse to keep at tenpai than an outer one.
Kanchan vs Penchan
While kanchan and penchan wait on the same number of tiles, a kanchan is considered better to keep, because a kanchan has more upgrades. This is similar to how inner kanchans are better than outer kanchans.
- A kanchan can be upgraded by drawing , turning it into a (two-sided) ryanmen.
- A penchan cannot be upgraded to ryanmen on its own. It must first draw a , turning it into a kanchan, then draw the to get a ryanmen.
As a kanchan requires 1 drawn tile to be upgraded to a ryanmen, but a penchan requires 2 drawn tiles, the kanchan is superior to keep before tenpai. In addition, only a kanchan can be turned into a ryankan shape, adding another advantage. However, once you reach tenpai, both kanchan and penchan become effectively identical.