|Manga||001. An Incident|
|Manga||023. Normality (seen in flashback)|
Masashi Yamada was a teacher who arrived for the Onion Alien Mission.
Masashi Yamada is a male in his early to mid-30’s. Due to his profession, he dresses formally; a dark suit, black pants a white shirt and a tie. He also wears glasses and a pair of dark shoes.
Yamada is a very sociable person. Encouraging others to introduce themselves and he takes the initiative and starts doing so.
He taught first graders at Nerima Elementary school. He died on his motor scooter in an accident and was then transferred into the Gantz room.
He appeared in the room before the Onion Alien mission and asked the others to introduce themselves with their names and stories. He was skeptical of the idea that everyone in the room was dead, and came up with the notion that the whole thing was part of a TV show with hidden cameras, being pulled of by means of hypnotism.
As they are transferred out of the room, the middle schooler Joichiro Nishi tells him that it is indeed a TV show and that they can win 10 million yen which he exclaims, forcing Nishi to tell the others whats up, he then runs off along with the two yakuza and Takashi Inamori, he finds the Kid Onion Alien and is then joined by the other three, but the alien gets away after squirting mucus on them, they then chase and despite Masaru Kato protestations they kill it, after which its father shows up and proceeds to killing the four of them, he does this by cutting off both of Yamada's arms. Then while dying, he dreamed that it was all a fake TV show, and that everyone was still alive and well. However, he soon wakes up and screams in horror when he sees his arms are gone. He then bleeds to death, still clinging on to the hope that he'd be transferred back to the Gantz room again.
- In the anime, all mentions of his speculations on the Gantz room being a TV show are removed. Also, Nishi never tells him about it actually being a TV show, since his story in the anime was changed to him being the son of "Vice-Minister Nishi" and that the aliens and guns were all real.
- He was the one who accidentally killed Hatanaka in the anime due to panicking. In the manga, it was Inamori who shot first.
- Another difference is that his delusion of being perfectly fine after the alien cuts off his arms is not present in the anime, so he dies immediately afterwards instead of saying that he wants to go back to the room.
- In hbi2k's Gantz: the Abridged Series, his name is Joe Salaryman. And he is very well received and liked by all.