|Family||Hisashi Sakai (father)|
|Live Action|| Kento Hayashi
Iori Ashihara (child)
A second-year middle school student and member of the MDC. He started diving after being deeply impressed when he saw Youichi as a child and he is very inspired by Youichi. He does things at his own pace and truly loves diving, but in his heart hides a strong will, and he never gives up.
Appearance EditHe has short black hair and diamond blue eyes. He wears blue swimming briefs when he's diving.
Tomoki likes to do things at his own pace. He is said to have a strong will. He is diligent, persistent, and he has a good heart, and he always tries his best.
Youichi Fujitani - The diver Tomoki looks up to. They met 6 years ago, and Youichi's skills inspired Tomoki to begin diving.
Miu Nomura - Tomoki's ex -girlfriend. She confessed to him in their first year of middle school and they dated for a short while. She still likes him and some people still think they're dating but that isn´t true. Tomoki sometimes didn´t want to talk to her because he still doesn't know why he said yes to her.
- He has a dog named Chikuwa. Tomoki's brother Hiroya found Chikuwa 6 years ago. He was named after the Chikuwa he likes to eat.
- Tomoki is double jointed, making him extremely flexible.
- Tomoki's special ability are the "Diamond Eyes," the ability to recognize objects in great detail while moving at high speeds.