Pg26
If you know your Sengoku History, you'll know that Hidetsugu is only the nephew of Hideyoshi. Meanwhile, Hideyori is the actual child of Hideyoshi. Meaning that Hideyori shares more blood with Hideyoshi than Hidetsugu. So if Hideyoshi doesn't get reborn then the next in line to inherit Mikoto (Hideyoshi's Oni) is Hideoyori.
But the fact that Hidetsugu is in possession of Mikoto and not Hideyori means that Hidetsugu must have killed Hideyori so he can inherite Mikoto. That is why Chikahito think it is scary because he realize that Hidetsugu killed Hideyori.
I don't get wat happened on ch3 oh 26 can someone explain the boy worth the glasses said it was scary somehow