Unrequited Boys Be

Good boy

Once you read both chapters, it becomes clear that Amasaki is
involved in a nasty, sadistic relationship with her younger step-
brother, Binta (who's her "little piggy").

I think she has serious "daddy issues." Her parents probably got divorced,
and Amasaki resents her father for that (especially if something like abuse
or adultery was involved). Or maybe she's upset simply because her father
always told her he loved her (implying he would never leave her and the
family).

Whatever led to Amasaki's bitterness toward her father, she takes it out
on her poor little stepbrother, who's a constant reminder of the divorce
and remarriage.

As Feronen notes, you must read the
prequel, Absolute Midnight, in order
to fully comprehend this chapter.

Thank you for pointing that out. It makes
this chapter much easier to understand.