Kumagai was a physician and Starfleet officer in the 24th century. He graduated from Starfleet Medical Academy in late 2373, with a specialty in burn wounds. Upon graduation, he was given the rank of Ensign and assigned to the USS Lexington. In 2374, during a battle in the Setlik system during the Dominion War, Kumagai was incapacitated when the Lexington's sickbay was breached by a Dominion strike. (SCE eBook: War Stories, Book 1)