Maki Sanjou

Sanjou Maki is the girl living next door to Sakonji. She appears to be well-bred, gifted with both beauty and brains. However, one night, Sakonji sees her masturbating on the veranda.

Maki easily admits that she's a dirty girl and jokingly suggests to Sakonji that she should be blackmailed into being his sex-slave.

(Source: call-it-anything.net, AnimeNFO)