Natsu e no Tobira

While most of the students at Marion Fiesse's boarding school have left for the summer, Marion and several of his friends have decided to stay on campus. Calling themselves "rationalists," the group prides itself on upstanding behavior, and never letting their emotions get the better of them. However, everything changes when Marion meets Sarah Vieda.

It does not take long before Sarah seduces Marion during a rainy day, and the two enter into a physical relationship despite their large age difference. While Marion gets swept up by his first romance, he has no idea how much this newfound experience will forever change the lives of both him and his friends.