The Shinsengumi was a military police unit in Japan during the Meiji Restoration. Okita was one of its most skilled members, known for mastering the Tennen-rishin ryu sword style. He served as captain of the First Unit and frequently collaborated with Saito in battle. In the OVA, Okita played a significant role in the Ikedaya Affair, which took place in 1864. During one of his encounters with Kenshin, he admiringly commented on how much better Kenshins Hiten Mitsurugi-Ryuu technique had become each time they crossed paths.