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.
In addition to shaking his world-view, Keiki's encounters with the abnormal have led him to conclude that neither Sayuki nor Yuika are the elusive Cinderella. Through process of elimination, the only one remaining is Mao.
Keiki continues to receive mixed messages from Mao. Could she be the elusive Cinderella, or is she in love with someone else? Keiki decides that he must confront Mao directly to find out.
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.
Keiki works with Koharu to help her win Shoma's heart, but Keiki's attention is diverted by another Cinderella suspect - student council vice-chairperson Ayano Fujimoto. Could she be the one, true, non-perverted secret crush?
Another Cinderella candidate turned out to be a pervert. Keiki must now turn his attention away from his own concerns and help Koharu. She must find the courage to tell Shoma her true intentions - and her true age.
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.
The Cinderella panties have gone missing, prompting Keiki to step up his investigation. As a first step, he decides to spend a day with Sayuki - on a date, not as her friend or kohai, but as her master.
Keiki's attempt to seach for evidence in Yuika's underwear drawer backfires terribly, but he is still able to investigate her. Can he finally confirm Cinderella's identity?
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.
