Guillered♂

Capable of traveling between worlds, Guillered is the one who created Laughter Land and is responsible for bringing all the boys there. Although his exact intentions are left to speculation, he attests that his purpose is only for the happiness of everyone. At least, his sweet, playful demeanor does seem entirely genuine, and his kindness is far from suspicious.

[Edited from Eroderekko's blog]

His gem is located on his left hand.

(spoiler hidden)