I think it makes sense to name Saeki on the paper. He didn't operate, but he's in charge of the whole department, so it's typical to put his name as last author. The whole team involved in the surgery was listed too, including the nurses, so I think it's just part of showing that this is a case report about a patient in Saeki's department. Takashina is still listed as the actual first author, at least. I suppose Tokai must have asked not to be listed, or else Takashina didn't even tell him about it at all.

A second season would be great :D