Gantz reaches its apocalyptic conclusion The alien invaders have been defeated, but aboard their goliath orbiting mothership, their final champion sends a challenge to Gantz warrior Kei Kurono: face him in single combat or the mothership will plunge to Earth, decimating the planet Hiroya Oku's Gantz is adult manga at its most challenging: violent, bizarre, erotic, and created with stunning craft and fierce imagination.