There's the confirmation. Shikimi is dead. Next to die among the bullies is either her "friend" or the fatso, no way ringleader Okaya is next. I'm surprised at how quickly they jumped to the conclusion that both missing group members are already dead, since I don't think even Kowase's corpse has been found, and no way anyone other than Mari has seen Shikimi's dead body at this point.
Regardless, Okaya is sharp enough to suspect Kiritaka's parents, but I think he'll go into conflict with Taiichirou first since his ex-wife not only changed both her looks and identity, but is also out of town. Mari remains a few steps ahead of her enemies for now.