Well, the previous chapter did start with a shadowy figure with talon like nails behind him, poised to strike. Then an abrupt shift to Yamai being narrated and internal monologuing, I don't think it'd be wrong to say we were supposed to have some idea of what happened to him.Ah, nice twist. It wanted you to think he stayed home because of sickness but it was actually because he was kidnapped by a crazy person.