Mitsuru is a diligent and focused young boy who practices kendo. He really cares for Tsubomi and will often get jealous if anyone happens to gets close to her.
- Hanasaki Tsubomi - Mitsuru also liked Tsubomi, and tried to protect her since he was little. He couldn't bring himself to confess his feelings for Tsubomi, however.
Prior to the series, Mitsuru met Tsubomi after spotting her being intimidated by an senior student and attempted to protect her. Since then, the two became friends and Mitsuru can always be found either helping or protecting Tsubomi. On the day when the Hanasaki family began moving to Kibougahana, Mitsuru was hidden behind a street corner, too heart-broken to say goodbye to her in person. He notices the music box that Kaoruko had given Tsubomi fall out of the van and tried to give it back, only for the van to be too far away. He held onto the music box since then in hopes to give it back to Tsubomi one day.
A few months later, Mitsuru meets Tsubomi again, who comes to visit Kamakura with Erika and Itsuki. Mistaking Itsuki as a boy, he acts unfriendly towards her out of jealousy. When visiting a lavender garden, Itsuki catches Tsubomi who trips over a branch, which provokes Mitsuru's jealousy even more, even rushing ahead of them upon hearing how Itsuki calls Tsubomi by her name. This provides a chance for Sasorina to seize his Heart Flower and turn it into a music box Desertarian. In his Desertrian state, he confesses how he was unable to catch up to the Hanasaki family's car and return the music box, hence carrying the guilt for a long period of time. After being restored to normal, Mitsuru blushes upon seeing Tsubomi's face, but then he changes his mind about confessing to asking if he can meet her again after the box plays a melody.