Welcome to Gafuno, one of Tokyo's wards held hostage by an all-out paint war between two rival mega corps, Lacus and Sinus. Their weapons? Magical, color-wielding beings called Shikkon.

High schooler Urumi Ichinose wants nothing more than to graduate and escape this color-vomit hellscape. But when Sinus Corp threatens to shut down her grandfather's shop for refusing to go red, Urumi has no choice but to fight back.

But how does one high schooler fight against mega corps?

Urumi's answer appears in the school toilet. A leech-like Shikkon proclaiming itself Puro emerges, latches onto Urumi, and grants her the ability to paint anything blue.

If the corps want a war, Urumi and her new toilet-dwelling companion will give them one. "SCREW THOSE CORPS. I'M PAINTING EVERYTHING BLUE!"