100 years in the future I woke up on the 50th basement floor of the "Otsuka Metro", a labyrinth full of metro beasts, in Tokyo, which was transformed by "the flooding of the metro" and "contamination of super fungi".

Still, Satoshi stands up with his partner, the Chipmunk Tamiko. Eat the spores of the defeated metro beasts to level up and acquire "bacterial ability (skill)". An adventure begins with one person and one animal to escape to the surface.

"Shin Tokyo" is a country that was reconstructed from the catastrophic collapse caused by the "Tokyo Referee". A hunter spun in a new world...