Private First Class Katsuhiko Kumanosuke "Mac" Takahashi is the technical expert of the Rapid Response Tactical Squad and a supporting character in the 2005 film Doom.
Mac left university to join RRTS. He isn't shown to be talkative unless talked to first and does not stay in the fighting long after being called away to rejoin the rest of the squad after Goat's death by Dr. Willits.
He was then "killed" in the Archeology Dig while being told to stand by for orders, by decapitation from the Hell Knight.
It was later revealed a fan theory confirmed by Mac's actor, Yao Chin, that immediately after the squad found the deranged Dr. Todd Carmack and went back to their mission, Samantha Grimm asked him to wait for a second, so she can inject what she said to be a "flu shot" (Chromosome 24) into him, and after that was done, she gave him a cloaking device during his mission, which he appreciated the offer from her. It was also later revealed that not only the C24 serum determine whether or not the host is "good" or "evil", but can also sense that he/she could be on the "neutral" side as well, but unlike the other sides however, granting them the ability to cheat death itself, and even after the Hell Knight decapitated him, his head immediately reattached itself, and he realized that not only were the others after his "killer", but he was also the first squad member before Reaper himself to discovered some of the C24's affects on him. He then went back to the UAC base on Earth, only to encounter and killed the mutated version of Huengs (who apparently became the Revenant). Once all of that was done, he turned himself invisible, and went with Reaper and Sam when they are riding on the elevator back to the surface together.