From Hoshikuzuu Scans:

For certain reasons, Kuroe from the computer arts department at Mishima School of Design, has gone to Kishima from the fashion department to commission a costume for cosplay. However, the commission fee is 100,000 yen too expensive, putting Kuroe in a pickle. But Kishima says that he'll waive the fee if Kuroe will become his model. Thinking that it's such a sweet deal, Kuroe unknowingly agrees, but the outfit he is modeling turns out to be a full-body skinsuit. This is the start of a mutually beneficial battle full of faint beatings of the heart.

Daiki, a university student, fell in love at first sight with his beautiful, black-haired classmate, Mitsui. One day, when he went to a goukon, he sighted a person near the store who looked like Mitsui. After Daiki had followed that person, what he saw was...?!