My Sister Was Always Beside Me (妹はずっと、そばにいたImōto wa Zutto, Soba ni Ita) is the 12th episode of the Kono Naka ni Hitori, Imouto ga Iru! anime series.
After their date, Miyabi, kissing him by surprise, asks Shougo Mikandono to be her boyfriend, but he turns her down and she tearfully storms off. Shogo and Ikusu later turn to Yuzurina, who is really a child actress named Nayuri Danno, who played as Perin in "Transforming Warrior Granberion", learning that she is working with Seri to alter the results of the DNA tests to create a scandal since Miyabi is his true younger sister. Shogo hears word from Mei that Miyabi had an accident during her pool practice and was sent to the school's infirmary. When he goes to see Miyabi, she reveals that she was the one who asked Shogo to marry her back at the funeral, and she was only trying to hide her sibling relationship with him so that they could be lovers. Yuzurina was the one who coerced Miyabi to dispose of a letter containing evidence of her sibling relationship with Shogo, deceiving Miyabi to convince Shogo to be with her. Shogo reveals Yuzurina's true identity and nature to Miyabi, but he also reassures that they will remain as siblings, forgiving her for all what has happened. Some time later, Shogo and the other girls congratulate Miyabi over her performance during a swim match, while Ikusu fails to locate Yuzurina. Then, Shogo gets chased again by the girls after their argument over him.