[kari-no-sugata II]

Forgot to reply to this earlier:

Originally Posted by tsunade666

Oni didn't ended up a massacre beyond the mountains. the part where he was forced to eat his sister isn't there too. He just ended up having kin eater. that was sad and evoking in WN when the tamer forced him into it.

He was still forced to kill and eat his sister in the LN. See chapter O5 from LN8:

Spoiler for not for the faint hearted:

Because that place doesn’t exist anymore. I lost everything. My family, my pride, everything. I have no right to go back there. Not after I ate my own sister…

“Kill.” That voice gave me an order. I felt myself squeezing a small, skinny neck.

“Eat.” Another order. My fangs tore into skin, and the taste of blood filled my mouth.