Haruka Yasaka, younger brother to Kazuki Yasaka by five years, sports light brown hair often tied in a ponytail and distinctive purple eyes. A childhood car accident left him using a wheelchair after he chased Kazuki, who was fleeing to find his biological mother.

Deeply kind and devoted to Kazuki, Haruka idolizes TV personality Sara Azuma, believing he receives personal selfies from her—unaware "Sara" is Kazuki crossdressing to indulge his admiration. Discovering the truth, Haruka fears he stole Kazuki’s genuine smile.

His longing for connection drives him to share "Sara’s" secrets with Kazuki and send "Sara" a distress call when his pet Nyantaro vanishes. Playing cards with Enta Jinnai, Haruka admits Kazuki changed—losing his smile and discarding a vital friendship bracelet (miçanga). Haruka returns the bracelet to Enta.

Anticipating Sara’s Asakusa visit, Haruka is stunned when the real Sara doesn’t recognize him, exposing Kazuki’s deception. Flashbacks show a cheerful Haruka comforting Kazuki about his adoption before the accident. Post-meeting, Haruka apologizes via message for "stealing" Kazuki’s smile and confesses he sent away Kazuki’s biological mother, fearing abandonment. This intercepted message leads Reo Niiboshi to kidnap and confine Haruka until Kazuki, Enta, and Toi Kuji rescue him with Keppi’s aid.

The brothers reconcile, with Kazuki vowing to strengthen their bond and find his mother. Haruka later voices concern for Enta and shares a drawing hidden behind a Lionel Kappa poster, triggering Kazuki’s memory of meeting Toi. He confides in Sara about love and desire’s fragility, symbolized by a shattered headdress omen. Witnessing Sara transform into the Princess of the Stars and depart with Reo, Mabu, and Keppi, Haruka learns perseverance in desire, love, and hope.

In the epilogue, Haruka becomes the frog-themed idol Asakusa Keroppi and appears to regain leg mobility.