Hasuno Saki

Tooru’s childhood friend and Keiko's classmate.

She used to be a good, honest girl, but after a certain point she became Tooru’s little sister, and turned into a scary girl who entangles her brother in her wiles. (According to Tooru.)

And the scariest part is that she does so almost unconsciously, so her brother is always troubled.

With circumstances being what they are, it’s not that she has a complex towards her brother.

Incidentally, her family are rich landowners.