Contrary to popular belief, you can play mahjong with only three people. All you have to do is take out one-fourth of the tiles out of the game. This can be approached two ways: part of a numbered suit (say 2-man through 8-man) and an extra random six tiles after the walls are built are removed or an entire wall is removed with random tiles that was supposed to be in that 4th wall. It’s not really as complicated as it sounds.
In Tenhou, 3-player games are done following the first approach as mentioned above. In addition, North tiles are treated as a bonus tile (not dora necessarily) in which you can opt to use to draw from the dead wall. Also, hands values are capped at 24000 instead of the usual 32000 (increase each value by 50% for dealers). Which leads me to the picture I was meaning to show:
