She’sn ～シーズン～

She'sn (aka "season") is a visual novel love adventure game which focuses on a four different stories through all four seasons. The player can select to play the story of any season in any order. Different season also features different heroines and different love stories to play through. The spring story revolves around a forbidden love with your sister-in-law. The summer season tells the love story with your childhood friend. Love story in the fall is about the school romance. And the winter season is a sad love story between the protagonist and a girl with an incurable disease.

[from MobyGames]