Manatsu no Tobira ~Kimi to Tsuzuru Monogatari~

You play as a character asked by his sick sister to share with her a picture book that he made. Inevitably, this leads to romantic entanglements with a group of young girls, including Yukina Sakura, Yun Kitami, Nanami Mizuhara, Kaori Kashima, and Mayuko Hatuse. [taken from IGN.com]