We don’t know who invented Japanese-Peruvian cuisine (our guess would be Japanese-Peruvians, but we’re not culinary anthropologists), but we’re glad we finally got some of it in Boston. Ruka is a place where you can get sushi made with plantains and short rib in addition to hamachi, and you can get it while enjoying egg white cocktails in a buzzy Downtown Crossing restaurant with a lot of people there for Happy Hour or a pre-theater meal. The dining room’s faux stone carvings and snake sculptures may give you flashbacks to Legends Of The Hidden Temple but you probably always wanted to be on that show anyway, so it works.