Ryota Kohama

2003 they took a break to improve their abilities. They merged into a new group with seven other members and were called GROUND 0.

In 2005, when Toru tried to explore acting and took a main role in the TV series Shibuya Fifteen, Ryota also played a minor character in the drama.

That same year, he was invited by Toru to form a rock band, alongside their upperclassman Alex and Toru's friend Yuu Koyanagi. In the beginning, Ryota initially had no interest in joining a band or playing bass, until he listened to Red Hot Chili Peppers and was inspired by Flea to play bass. During the early days of ONE OK ROCK, Ryota only talked to Toru because he felt inferior and didn't talk to vocalist Takahiro Moriuchi for about a year because he was afraid of him. He was the most furious when Alex was caught groping a schoolgirl on a subway and almost quit playing bass to learn to play guitar. Ryota collaborated with drummer Tomoya Kanki and wrote the song "Deeper Deeper".

On 18 February 2017, Ryota married Michelle Lavigne, the sister of Canadian singer-songwriter Avril Lavigne. He has one daughter, born in October 2017. The couple announced their separation at the end of September 2025.