mihimaru GT's hiroko digitally released her solo single "Super Rainbow" on June 5.

mihimaru GT has been on an indefinite hiatus since 2013. After seven and a half years, hiroko had announced that she would be resuming her solo activities, and "Super Rainbow" is her comeback song. On the song, she commented, "It's a song that will help you move forward with a strong message that says no matter what happens in the world, you have the choice to plow through."