Responses
I think its because kid Tsukasa love Amane and threw his life just for his beloved twin so the spirit who took tsukasa form and thought that tsukasa has some kind of obssesion with Amane... I think
It probably amplified his love in a twisted way. I don't think the spirit itself is very interested in Amane. Probably. I really want all the chapters to be out to binge it all maaaaan (〜￣△￣)〜
I think I'm beginning to understand Tsukasa, I've neglected to mention how different he was before he was spirited away. He gave himself up to the spirit of the house to cure Amane of his sickness, and in return it seems like the spirit possessed him. So this is most likely the cause of his twisted ways, and his weird obsession with Amane. He had definitely loved him lots before, but now it's kinda smothering. Whether his violent tendencies are a natural thing or not, Amane probably felt something dangerous about Tsukasa and possibly killed him because of it. Self-defense? Desperation? Who knows. Tsukasa is a different boy from who he was, like his mother had said.