Saikin, Imouto no Yousu ga Chotto Okashiinda ga.

Synopsis

Mitsuki asks Hiyori if there is a way to change the design of the chastity belt to which she responds by saying it will be fine the way things are. She then upsets Hiyori by bringing up why she isn't doing much herself including trying to remember more about herself which causes her to leave in anger. As the day goes on Mitsuki is happy to finally get time for herself but by dinnertime feels guilty and upset. Yūya notices, and during dinner is able to make her blush by his kindness which confuses Mitsuki as Hiyori isn't around. With her heart throbbing thinking about him, Mitsuki then puts her head on the table. Thinking she is choking Yūya picks her up and performs the Heimlich Maneuver, which causes her instead to have an orgasm. Embarrassed when asked if she is okay, she slaps Yūya leaving him confused. Mitsuki heads to the bathroom where she continues to be confused on why her hearts still throbbing for him, she begins to think of love but then denies it in her mind. When using the bathroom she notices the chastity belt is gone, in a panic thinking that Hiyori has crossed over she goes out looking for her. She tries looking to no avail until Yūya who has been worried looking for Mitsuki shows up. He agrees to help her look for her lost friend who she had a fight with to her relief. She finally finds Hiyori in the place where Mitsuki first collapsed and asks her why the chastity belt disappeared, while smiling Hiyori places it back. Mitsuki goes to a nearby bathroom where Hiyori explains that she had a new chastity belt made for Mitsuki as she wished and that it never truly disappeared fully. Mitsuki makes up with Hiyori when they get home but is mortified at the new more revealing belt design preferring the old one. Yūya is last seen in a convenience store asking if anyone had seen a girl with a big ribbon in her hair with wings on her back.

(Source: Wikipedia)