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)

It is unclear whether or not Kumagai was one of the numerous casualties of this battle. He was named after "Painless" Kumagai, the medical examiner from the Scott Turow novel Presumed Innocent.

USS Lexington personnel
USS Lexington (NCC-1709)	J. Baila • Berriman • P. Coss • D.W. Davidson • W. Driveon • G. Franklin • Tivra Ivari • Garth of Izar • F. Haverty • Ito • T. Ivari • L. Kelso • Korolev • R. Leslie • W. Manyard • W.C. Perinal • D. Ralston • M. Rousseau • W. Samuels • P. Sh'vaohran • D. Sinclair • L. Sterling • C. Stuart • M. Trellan • J. Turnman • N. Uhura • V'Shall • M. Wanglestien • D. Watley • R. Wesley • A. Wilson • W. Worrenstill
USS Lexington (NCC-14427)	Declan Keogh • Manojlovich • Rosita Pérez
USS Lexington (NCC-61832)	T. Allenby • H. Anderson • Antonacci • Audrey • G. Ben Zoma • Bowdren • T. Cadwallader • S. Carson • Cavanaugh • J. Cox • Eberling • Fornnel • Gaines • F. Galloway • Griscom • Halprin • Hasegawa • G. Jenson • P. Joseph • Kumagai • Leff • E. Lense • R. Mithra • Moytulix • Pridemore • Rodgers • Soriano • J. Turner • Twistekey • Man-Fai Wan • Wilhoite
USS Lexington (Steamrunner-class)	A. Jago