Max Hell, a lone samurai, is on the trail for the Serum which was unleashed to turn all of humanity into Toads. Yep.

Fun fact! The film Toad Warrior was initially released to Malaysia, the Philippines, and Japan for theatrically presentation only. This film was never supposed to be released in the U.S. as the filmmaking team of Jackson and Shaw never liked the final cut. For this reason, they held back on its U.S. release while they went on to create other feature films -- planning to eventually reedit it. During this interim, somehow a distribution company got hold of a copy of Toad Warrior and illegally released the film. Eventually, this version was taken off the market. But, as the film was already in wide distribution, all Scott Shaw could do, to protect the integrity of the film, was to release an Official Version of the movie - Max Hell Frog Warrior.

https://en.wikipedia.org/wiki/Max_Hell_Frog_Warrior