Aizawa's dead old friend. Decent guy, liked cats. Corpse used to create Kurogiri (that handsome bartender).
Who da fuck is Oboro Shirakumo
Short for "Grow Up You Baby". You see someone on the internet complain about some childish thing? Hit em with the GUYB.
A: "Kathleen Kennedy ruined Star Wars waaaa"
B: "Oh, GUYB and get a life"