Age: 17 (second-year), 18 (third-year)
Birthday: October 30th
Height: 181 cm (5'11")
Family: Mom (Kanade Abe), Dad (Masao Koshiro), Twin Brother (Mamoru Koshiro)
Background: His mom and dad fought a lot growing up. When their mom's affair came to light, they eventually got a divorce. Miyabi and Mamoru who were inseparable growing up ended up being separated. Mamoru lived with their dad in Osaka while Miyabi stayed with their mom.
— They went to two different middle schools as a result. At his middle school, Miyabi got involved with nasty delinquents and swiftly rose to a position of power.
— When Mamoru got injured & hospitalized, Miyabi felt immense guilt for not being there to protect him. Therefore, straightaway, he moved to Osaka to live with his dad, and also properly be there for his brother who was the only person he treasured in his family.
— On the sideline, Miyabi was dead set on figuring out who hurt his brother so he could get back at them. Once he pinned it on Ryu, he easily used Daichi (who was once a member of his delinquent crew in middle school) to hurt Ryu (and inevitably Reina) without a second thought.
Fears: Losing Mamoru
Trivia: Is the main comic relief throughout the story. Then, he becomes the main antagonist.