No, Nanai mo Ienakute… Natsu is not the Road Avenger song. I only mentioned it because it was their biggest hit, sorry if that was confusing. I should have been more clear. It’s a catchy song too though, so give it a listen if you haven’t yet. I updated the video so it should actually play now.

As far as the official title of the opening theme goes, I’ve only ever seen it referred to as the intro theme to Road Avenger or Road Blaster. As far as I know it doesn’t have a name other than that. Sorry I couldn’t be of more help. If you do find an official name for it, please let me know, I’d be curious to find out!