In the outside world, Nishi is considered a social outcast. He's picked on and considered a freak. However, when Gantz calls he's a cocky veteran who doesn't care about anyone but himself. He manipulates other hunters and always uses the invisibility device to stay nearby until the perfect strike shows itself.
The Onion Alien Mission
He is the only hunter
who has any knowledge of what's going at this point. He convinces the group that they are all on a TV show with a great grand prize which was more than enough to convince them. Shortly after he disappears for most of the mission using the invisibility device. Although he isn't seen for the following chapter he does say he's been watching the whole time. He reappears just after Kurono
beats the Onion Alien
to a pulp by shooting it with the Y-Gun
. He tries to convince Kurono to kill it with his X-Gun
and even saying that Kurono was just like him. He implies that he likes looking at pictures of dead bodies and that the suit makes him feel powerful. After Kurono calls him a freak and a loser and doesn't do it to prove a point, Nishi sends the Alien away with the Y-Gun. When they return to the room
he is surprised by how many survivors there were and tells them the sphere's name is Gantz
. He also tells them he's been doing this over and over for a year now and he knows more about Gantz than they do but he doesn't know everything. Kato
, being the oppisite of Nishi yells at him and blames him for everyone's death because he didn't tell them what was going on. After the mission Nishi uses the X-Gun to kill a cat but isn't satisfied and wants to go back the the room. He made 3 points for a total of 90 in this mission.
The Tanaka Alien Mission
When they all return to the room, Nishi asks to be sent first so that he can go invisible. Unfortunately, during the mission, he steps on one of Tanaka's birds alerting it of his location. The tanaka alien attacks Nishi and they both fall into the water. Nishi gets hit with a close sonic attack which breaks the suit. He begs for the other hunters to help but the all refuse. Kato suddenly jumps down the bridge to help him. Nishi gets hit with a second attack which pops his eyes, ears, and tongue. Kato then manages the kill the alien and bring Nishi out of the water. Thinking that the mission was over they both think that Nishi will surive but it turns out there was more than one. Kato tells Nishi by yells into his head so that it would echo in his head. Nishi starts yelling out for his mother then, after being only 10 points away, he dies.
Later in the series, someone shows Kurono a website that talks about a black sphere and aliens. Kurono figures it was Nishi's site since it stopped being updated with his death. Later in the series a reporter uses this site to track down Kurono since Nishi didn't bother changing names.
After the Oni Alien mission, one of the hunter receives over 100 points and asks Kurono if he wants to revive anyone. At first he thinks of Kishimoto and another girl but decides it's best if they bring back someone who knows a lot about gantz. So they bring back Nishi. Gantz shows Nishi his 0 points and he realizes that he died. They tell him he's been dead for over 6 months. Nishi recognizes one of the hunters who managed to get back in the Gantz room again.
The Osaka mission
During this mission he laid low as usual until the hunters managed to bring down the 100-pointer. Nishi then picks up the H-Gun and shoots it (and almost hitting one of the other hunters) At first it seems like he killed it until his arm is shredded. The hunters tie up his wound to stop him from bleeding to death and he is out for the rest of the mission.
End of the World
After the Osaka mission, Nishi shows them a counter. He says that it's a count down to the end of the world and that he's not sure what's going to happen.
Back to school
While walking to class his classmates throw his desk out the window and almost hit him. He threatens the class and takes another students table. The teacher leaves the class and the class take a vote on who wants Nishi to leave. All but one chubby girl who has a crush on him and even gives him a letter vote yes. After he laughs at them they manage to pick him off and take him to the window where he falls down. The class decide that they'll say it was an accident at that he was messing around then suddenly Nishi gets up. He looks up and says he's going up and they all better be there when he does.