Also known as: 坂井瑠星, りゅーせー, フクソウダッサイ
Real Life Japanese Jockey. He is one of two jockeys riding for Yahagi Yoshito's stable, the other being Furukawa Naho.
Horses Sakai rode in his career
- Bathrat Leon (Racehorse)
- Danon Decile (Racehorse)
- Dolce More (Racehorse)
- Forever Young (Racehorse)
- Lemon Pop (Racehorse)
- Loves Only You (Racehorse) - Only during training
- Mad Cool (Racehorse)
- Marche Lorraine (Umamusume)
- Melody Lane (Racehorse)
- Panthalassa (Racehorse)
- Ravel (Racehorse)
- Real Steel (Racehorse) - Only during training
- Shin Emperor (Racehorse)
- Stunning Rose (Racehorse)
- W Heart Bond (Racehorse)