Responses
logged in just six I could respond to this- THIS IS SUCH A GOOD THEORY. I think the fact that we say chi as a monster before we saw him in the womb with Ryota kinda messed up my perspective. He literally looks like an undeveloped fetus.
I have a theory after reading chapter 17. So if you haven't caught up, don't read.
Ryota warned his classmate not to talk to a dead person when they were kids - I think that's from personal experience. Since he said Chi was in the womb with him... what if that was his twin that he killed? I think there was a medical condition where one twin ends up absorbing/killing the other. And then the twin came back as a ghost and Ryota started talking to him, which ended up making the ghost more powerful. When the mom got pregnant again, the ghost ended up possessing the body of the new sibling.
And that is why the title is Ryota killed his brother. It refers to something that happened in the past (and maybe in the future, as an ending to this manga?)