My Sister and the Moonlit Dance (妹と月夜のダンス Imōto to Tsukiyo no Dansu) is the 2nd episode of the Kono Naka ni Hitori, Imouto ga Iru! anime series.
On the school rooftop, Shougo finds Mei Sagara, an upperclasswoman that dresses as a witch, who reveals that she works at a cosplay café. Later on, he encounters Ikusu Mizutani, a member of the Seiryu Association and initially introduced as Mister X, who explains that his father, Kumagoro Mikadono, had an illegitimate daughter after an affair, and it would be a scandal if Shogo were to marry this girl. Ikusu later transfers into the academy as a male student to keep an eye on him, and then stops by at his place to take a shower. At the student council dance party, after Shogo has a dance with Konoe, a confident Rinka Kunitachi, the student council vice president, challenges him to a dance, receiving quite an applause from the onlookers. Shogo finds a timid Miyabi outside, and he asks to have a dance with her, but the top of her dress later becomes undone. Luckily, Konoe finds the two, and she helps fix Miyabi's dress, much to Shogo's relief.