The main character of "Pen and Key, 10% na Boku etc." is Hinako, a female college student who is positive about everything. Feeling destined for Yui, a young man she met at the place where she moved, she asks him to become a model for her painting, but she doesn't get along with his reaction. Hinako doesn't give up and tries to get involved with Yui, but he has a serious secret that goes far beyond imagination...