One day, Hiroto suddenly discovers a mysterious power inside him and transforms into Zima, in order to fight to protect the planet he loves against a bizarre slew of hostile aliens. from Manga Reborn

...rough and tumble boxing action as Ken, a fighter with a sad and muddled past, battles his way to finding the true meaning of his return to the fray. The love of his life has married his rich rival while he was away, and as he deals with the harsh sting of reality, a girl from his past returns to lead him back to the path of honor and dignity in boxing. But will Ken even want to follow it after all these years of loss?