J. Katayama

"What are you doing here? You're gonna attract attention and then they'll come."

- J. Katayama to the Marine

J. Katayama was a maintenance worker in Doom 3 who was stationed in the Caverns area. He was one of the few personnel who survived the initial demon invasion.

The Marine finds him in the thermal regulation pumps, hiding away from the demons. He refuses to come out until he's sure that all of the demons are dead. Katayama offers the Marine his key card and then pushes him to get out quickly, since the Marine is making too much noise. He is the last survivor the player meets before the ending of the game.

His fate is ultimately unknown, but he presumably perished along with the whole of Mars Base, as Resurrection of Evil states that the Marine was the only known survivor of Hell's invasion.