美少女万華鏡 -かつて少女だった君へ-

In the middle of the mountains stands an isolated, rural hot springs inn. There works the beautiful waitress, Inamori Haru. Kamijou Souta, the lover of Haru, secretly pays a visit to the inn in order to surprise her... This is the story of a night of passionate love woven by a foolish couple of adults who have fallen in love... [Translated from the homepage's official synopsis]