Based on the manga Salaryman Kintaro. There`s also a game with the same name. And a live-action series. But this is the anime, by Emotion (Bandai Visual) "It`s about Kintaro, former leader of a widely feared and respected biker gang, who decides that its time to `straighten out` and become a `salaryman` since his wife died and he has to take care of his young son." Sounds similar to GTO, but it isnt. Well, it is a little similar, but its original. I`d say its more like a modern day anime version of "Lone wolf and cub" then it is a GTO copy.