Concealed hand

A concealed (or closed) hand is one in which the player has formed every meld from tiles they drew themselves, without claiming any discard via chi (chow), pon (pung), or an open kan. The hand stays hidden behind the rack until the win, and a concealed kong made entirely from self-drawn tiles still keeps the hand closed even though it is laid down face-down. Calling a tile from another player to complete a meld immediately makes the hand open and forfeits the concealed status.

Concealment carries significant scoring weight in nearly every variant. In Japanese Riichi it is a prerequisite for the central riichi declaration and for several yaku — pinfu, iipeikou, and the closed-hand version of menzen tsumo all require a fully concealed hand, and winning on a discard while closed adds the menzen ron 10-fu bonus. In Hong Kong scoring a fully concealed self-drawn win earns extra faan, and Chinese MCR awards points for 'Fully Concealed Hand' (self-draw with no melds called) and a smaller value for a concealed hand won on a discard.

The trade-off is speed versus value: staying concealed keeps your hand flexible and worth more but means you cannot grab useful discards, so you depend on the wall. For example, holding 4s5s and needing 3s or 6s, a closed player must draw it (or ron it on the winning tile) rather than chi it from the left. A common confusion is that the concealed self-draw distinction matters: a closed hand that wins by ron is still concealed for most purposes, but in Riichi the special menzen tsumo yaku specifically requires the winning tile to be self-drawn, not claimed.