It's about Izayoi's and who possibly killed him, just another warning
I'm lead to believe and am 90% sure Ruruka killed Izayoi. I'm convinced his forbidden action is eating sweets or something and that Ruruka, after the Seiko incident, either forced and while he was still asleep, made him eat something and he died. He isn't killed like every other victim and he has a tiny amount of blood coming from his eye, like Bandai after he was poisoned. Kirigiri wipes something from his body and i'm guessing it's foundation used to cover up the blood and veins and horrors of the poisoning like Bandai. Also Seiko is missing the knife in her chest that is now magically in Yoi's body. And Ruruka seemed to eager to leave the room and not wanting to be next to her dead boyfriend...seems a lot like Sakura and Asahina TBH