

Seeing how disturbed he is, Luka confesses her love to KAITO, and says that there is no way she would ever leave him. KAITO collapses just as Luka arrives at his place. Then, on a rainy day, KAITO gets triggered of his childhood trauma of someone getting stabbed. After Miku and Luka helped KAITO move into college, KAITO fell in love with Luka. When KAITO was orphaned, he was taken to live at a relative's house, but later left on his own and came to an orphanage. The trio's backstory, and how KAITO and Luka fell in love is revealed next. When she arrives, she discovers KAITO and Luka kissing. When KAITO's birthday comes, Miku notices on her way to KAITO's house that Luka hasn't been answering calls, so she once again doubts the promise. Luka notices how KAITO has been very tired and buying food mainly from the convenience store, so she and Miku decide to cook for his upcoming birthday. Additionally, Miku begins to notice how Luka has been coming home late frequently, which makes Miku doubt their promise. The trio enjoy their time, but Miku notices that the other two seem unusually close. When KAITO gets a day off, he takes Luka and Miku to an amusement park. Several years later, KAITO and Luka have gone to college together and have started working, but have also started a relationship behind Miku's back. Miku becomes afraid that she will be left behind, and makes a promise with Luka that the two girls will not confess their love. Luka says that she figured that was the case, but then admits that she loves KAITO too.

The following summary is based on the manga: The two girls and KAITO grew up together, and in middle school, Miku tells Luka that she loves KAITO. It is a song about a love triangle between the three. " ACUTE" is a song featuring KAITO, Megurine Luka, and Hatsune Miku by Kurousa-P.
