Keiki Kiryu is a kind-hearted high school student surrounded by attractive girls. One day, he finds a love letter with no sender information, other than a pair of panties. Keiki begins his investigation by speaking to his senpai, Sayuki.

Keiki's investigation reveals that the senpai he looks up to is a huge pervert, but it doesn't stop him from pushing forward. There are other suspects to interrogate! He approaches his kohai Yuika, a cute and supportive student librarian.

Keiki's search for someone who truly loves him, not as the object of a perverted fantasy, hits another dead end. However, another unsigned letter grabs his attention, although this time, it's blackmail.

With the situation between Koharu and Shoma settled, Keiki resumes his own mission to seek out the elusive Cinderella. Before he can do anything, however, Sayuki and Yuika drop by for a surprise visit.

A single photo and a simple change in perspective allows Keiki to deduce who Cinderella is. He begins an elaborate plan to prove it, and catch Cinderella with her panties on.

Until now, Keiki's concern has been about whether or not he can fall in love with a person with certain quirks. But now he must choose whether or not he is willing to jeopardize an existing relationship.