He joined Toei Animation in 1992, where he directed part of One Piece, Suite PreCure, and Sailor Moon Crystal.
After leaving Toei Animation and joining MAPPA in 2017, he has directed Zombie Land Saga, Mr Love: Queen's Choice, and Dance Dance Danseur.
[5][6] One Piece Film: Strong World won the award for excellence in animation of at the year and was nominated for animation of the year at the 34th Japan Academy Film Prize.
[14] In 2022, Sakai left MAPPA, and joined Studio Kai.
[2] Later, he directed and made the storyboard for third episode of 7th Time Loop which aired on January 21, 2024.