Masaru Katou has a good personality; he loves to help people and easily cares for everyone. His parents are dead so he is responsible for his younger brother who he is fiercely protective of. Katou usually takes the position of being a leader because he has good authority, but is unable to hurt others which hinders his performance in the game of Gantz.
Masaru Katou was Kei Kurono's childhood friend. They meet each other again the day they die because Katou was trying to help a drunk off of the train line, with Kurono reluctantly lending him a hand.