GANTZ

The story of Nishi and Izumi, before the events of GANTZ.

A special one shot that shows what Nishi does in his spare time.

The main character is named Nagatomo, he is an astronaut and a scientist in charge of a secret operation about experimenting cryogenics on human subjects such a assasins or political prisoners, all inside a spaceship called "RETRO". Suddenly he wakes up inside the ship only to see outside a huge amount of black spheres floating in space, he first believes they could the debris of something, then he realizes there is life activity inside them and leaves the ship to bring one of those spheres inside, then he proceeds to open it and founds a girl inside it, Kishimoto. Suddenly, Kishimoto is transfered along Nagatomo to a GANTZ room that looks like it's the Tokyo one, the black sphere inside the room starts playing the radio song and reveals the target, the "comedian alien", then sends both to the battle area. Kishimoto is wearing her GANTZ suit now but Nagatomo is only wearing his space suit, they fight the aliens (Kishimoto proves to be useful, because she knew about the missions) and are sent back to the room. The "Astronaut" gets 6 points and "Big tits" gets 0, Kishimoto decides to stay in the GANTZ room because there is no place she can go back, Nagatomo leaves but not before saying he will be back. Source: mangahelpers

A group of high-school students had an accident on their way to a trip and died but they find themselves in a classroom with a black sphere.

The manga's story begins when a peasant named Hanbee asks a girl named O-haru for her hand in marriage, but O-haru confesses that she is already thinking of another man named Masakichi from a neighboring village. When Hanbee seeks out Masakichi, he finds that Masakichi possesses a sword and the skills to use it, despite being a peasant. (Source: Anime News Network)

Reiko was raped during one of the Gantz missions, but she ended up killing her assailants - all evidence was erased after they teleported back to the room. *scat warning*

The cloaking/radar device given to the Gantzers along with the suit has some extra functions... perfect for a guy seeking to NTR. Well, you could use it to get any girl you want, but when you were originally a four-eyed nerdy virgin who's not destined to be the protagonist, you HAVE to do NTR.

Oku Hiroya tells in this manga what inspired him to draw GANTZ, and his love of Sci-Fi movies.