My Little Sister is Disciplined and Beautiful! (妹は、規律正しく美しく！ Imōto wa, Kiritsu Tadashiku Utsukushiku!) is the 7th episode of the Kono Naka ni Hitori, Imouto ga Iru! anime series.
Konoe Tsuruma and Miyabi became increasingly intimate with Shogo, as the latter fears of whoever he chooses between the two as his wife could be his biological little sister. As a precaution, Ikusu suggests of applying a DNA test on both of them, to which Shogo complies, with the help of Risa Seri, his mother's secretary. While Konoe agrees on taking the test, Miyabi strongly declines for mistaking Shogo as a fetishist. Afterwards, a board of directors come to inspect the academy's performance. While they have a meeting with Shogo, a person who claims herself as his little sister makes an announcement over the intercom and blackmails Shogo, threatening to expose his secrets if he tries to find her but also telling him to be wary of his surroundings. Finding this to be in bad taste by the board, as a response, the academy's student council appoints Shogo as their morality officer. As student council members act more strict over the students for their misconduct, Ikusu suspects Rinka as the one behind the blackmailing incident.