Christmas Eve night. Seto Kazuki was walking through the illuminated streets with his best friend Teratani. Today, they're at a Christmas party with Iori Reedzuki and Morisaki.

Kazuki fondly remembers the time when Iori was still only an admirer. The spring of his second year in high school, when he could only stare at Iori practising in the drama club...

Kazuki is suddenly confronted by his childhood friend Itsuki, whom he has not seen in four years, in his underwear. However, Kazuki's feelings for Iori grow, and he tells her that his relationship with Itsuki is "just a childhood friend".

On a school trip, Kazuki is alone with Iori and tries to pluck up the courage to confess his feelings to him, but just then a fire breaks out in Itsuki's flat and he receives a call that Itsuki has not been seen since...

Kazuki hugged a sobbing Itsuki. Since then, he is confused by his wavering feelings.

The photography club decides to organise a contest and Iori is chosen as the school's representative, but it is a trap set by Samejima and his friends, who were expelled from school for a voyeurism scandal. Iori is in danger in her swimming costume in an abandoned building. Kazuki, who was on a date with Itsuki, learns of Iori's danger and heads for the abandoned building. Then Itsuki decides to make a serious confession...

Invited by Teratani to a study camp by the sea, Kazuki meets Izumi Isozaki, a girl standing alone on a rocky beach!　He is shocked and depressed by her disdainful gaze.

Izumi tells him about a 51-stone spell that protects their love, and he decides to pile up the stones on behalf of Izumi's ex-boyfriend. And the last white stone he piles up is...

The day of the Christmas party finally arrives!　Kazuki confesses his feelings to Iori, but the drunken Iori doesn't understand his true intentions... Then, the after-party. Thanks to Teratani's consideration, Kazuki and Iori are left alone together. Kazuki is surprised to hear from Iori that he has been accepted into the theatre company. Meanwhile, Iori has to attend an audition at short notice at the request of the office..!

Kazuki is unable to tell Iori how he feels about her, and his feelings are becoming more and more urgent. In a mood of resignation, he gets on the train home with Iori, but the opportunity comes unexpectedly..!

After graduating from high school, Kazuki becomes a ronin and Iori joins Isai Productions to pursue a career in theatre. Kazuki and Iori start dating after he confesses his love to her on Christmas Day, but a commercial featuring Iori sparks his popularity and keeps him busy. They find it difficult to find time for each other, and their lives continue to diverge.

As if to take advantage of their discordant relationship, adults from Isai Productions press Kazuki to break up with Iori, and a person claiming to be the Marionette King posts messages on the internet suggesting that he is going to attack Iori...