Why isn't this Suu an Kou?

[Linsolv]

I\'ve been playing Riichi for a few weeks now, and I\'m finally trying to really get the yaku memorized, instead of my vague recognition of Ii Pei Kou and Tanyao..

So I\'m going through the \"Yaku Quiz\" in the web.

It showed this hand:

Concealed:


winning on ron:

That looks to me like Suu an Kou (4 concealed pon). Why isn\'t it?

(The quiz declared that it was NOT Suu an Kou, but instead Hatsu, Riichi, Toitoi, and San an Kou.)

(screenshot)

[WorTeX]

When declaring ron, the set which needed the last tile is considered open. With double pair wait, you can only self draw su anko, otherwise it only will be toitoi+san anko.

[b4k4ni04]

For determining whether a set is open or closed, especially for the last set. If it is acquired by ron, it is open, if acquired by self-draw (tsumo) it is closed.

[Johnstonjamese]

Now you know... and knowing is half the battle.

Now all you have to decide is the next time you get it, are you willing to give up the yakuman chance and Ron off of it ^_^

[Ignatius]

I agree with that, but. Can you answer me a thing?
How do you Ron other Yaku as Honroutou or Chii toitsu (seven pairs). If you do as you say you can´t Ron that. But you can. And Honroutou will not have it´s Han reduced by 1 if no set it´s exposed but you Ron with it.
If you can Ron that you always win 1 Han more for Menzen Tsumo (perfecly closed hand). But sometimes you win with those hands and you don´t earn that Yaku...

[Mcgreag]

You have to make a distinction between concealed hand and concealed set.

When you win on a discard the hand is considered concealed (if the rest of the and is concealed of course) but the set that is completed is considered open for scoring purposes (both han and fu).

In the case if Chitoitsu and Honroutou (for extra yaku) the condition is that the hand is concealed while for suuankou the condition is that the four sets are concealed. The pair is allowed to be open.

[Ignatius]

Thank you! now I see it more clear.