Mahjong Union
Mahjong Union (麻将連合, Maajan rengou; also known as µ (mu / myuu)) is a mixed professional and amateur organization of competitive mahjong players.
Membership
MU has 18 professional members. MU also has 35 "touring" members.
Projects
MU are apparently highly implicated in encouraging more grassroots promotion of online mahjong players with its "Three Arrows" initiative.