Kinnikuman II-sei: SP Densetsu Choujin Zenmetsu!

In 200X, Kinnikuman Junior (Kinniku Mantaro) forget to fight with all his heart, and instead lives a life of basic hedonism. At this same time, a series of outrageous incidents happen on Earth. Why are legendary chojin (known also as the Legends) are dying one after another in mysterious circumstances . . .? With only four Legends left alive, Mantaro must do all he can to help them. (Source: Kinnikuman Wiki)