Toshinosa Kyoudai to, Wasurerareta Yoru

In the near future, virtual reality (VR) has become widespread. The protagonist is an ordinary office worker who enjoys adventures in one of those fantasy worlds. He works at his company during the day and spends his evenings adventuring in the fantasy world. He has a younger sister who is a student, and a pro gamer, they used to get play together and party when she was young. Recently, however, she became difficult to get along with...... One day, as Christmas approaches, he notices a light leaking from his sister's room. She is in the middle of the Christmas event in the game and has been logging in for a long time lately. The protagonist tries to warn her to go to bed early, but He gets excited by the sight of his little sister wearing a VR headset and looking so defenceless. The protagonist, who loves his little sister, is so turned on by her that he ends up masturbating using her defenceless body as fuel......