Captured by a corrupt organization, the player has been subjected to tests which mutated them into a ghastly new form. To reclaim their human form, the player must explore the research facility and fight other mutants - "Neo Organic Bioforms".

The player selects one of seven possible forms and spends points to customize its abilities and attack powers along the way. Exploration is performed in first person, moving through the hallways in a fixed, grid-based system. Players can watch their minimap to track or avoid other bioforms. If the player encounters another mutant, the game switches to a tactical, turn-based fighting system. The player and the computer both try to target weak points on their enemy, with the winner of each turn shown attacking the other in an animated cutscene. The graphics are most noteworthy in using stop-motion puppets for all the bioforms, giving them a somewhat realistic look.

N.O.B. was only released in Japan, and was one of the few games published by Sanyo.