|This article is about a/an actor in Kamen Rider Zi-O.|
Gaku Oshida (押田 岳 Oshida Gaku) is a Japanese actor and dancer who portrayed Geiz Myokoin/Kamen Rider Geiz in Kamen Rider Zi-O. Until March 31, 2021, Oshida was affiliated with Ever Green Entertainment.
In November of 2016, Oshida was the winner of the 29th Junon Super Boy Contest and attended the contest alongside contestants Hiroki Iijima and Ryutaro Okada. made his first drama appearance in a live-action adaptation of the manga series Inside Mari. In mid 2018, he was cast as Geiz Myokoin in Kamen Rider Zi-O.
- Oshida is currently a student at Waseda University, studying human sciences.
- Oshida is a member of the street dancing club at his university, which he incorporated into Geiz's transformation pose and fighting styles.
- Oshida's skills include street dancing and skateboarding.
- Oshida has a driver's licence.
- According to Oshida, his portrayal of Geiz is inspired by many rival Riders of past series such as Kamen Rider Sasword and Kamen Rider Kaixa. He reveals that he relates more to them than the primary Riders.
- Oshida feels honored that people revere him to bear a resemblance to Ren Akiyama/Kamen Rider Knight. He met actor Satoshi Matsuda for the first time during the filming of Rider Time: Kamen Rider Ryuki. 
- Kamen Rider Heisei Generations FOREVER - Geiz Myokoin/Kamen Rider Geiz (2018)
- Kamen Rider Zi-O: Over Quartzer - Geiz Myokoin (Alternate) (2019)
- Kamen Rider: Reiwa The First Generation - Geiz Myokoin/Kamen Rider Geiz (2019)
- Kamen Rider Zi-O NEXT TIME: Geiz, Majesty - Geiz Myokoin/Kamen Rider Geiz (2020)
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- Oshida had won the 29th Junon Superboy Contest in 2016. The runner-up of the same year would be Zero-One-star Ryutaro Okada.