Ryouta is mostly like any other little brother; gets into arguments with his sister, tries to do school work (though with about as much success as Nagisa), and wants to show his parents he can be responsible. He also develops a crush on Honoka, always unfavorably comparing Nagisa to her.

Despite their regular squabbles, Nagisa and Ryouta care about each other very much, and Nagisa protected him when they were at an aquarium, and helped him to run an errand for their parents.