Ultraman: Is This a Band System or a Battle System?

Dual male leads, Belial and Fushion, plus the parents' love story, Kane and Mary. Read at your own risk if you mind OOC. Belial can probably be considered the counterpart of his parallel-world self. I'm terrible at writing introductions. Take a good look: this Ultra is Belial. One day, a band System suddenly appeared in his head. He hadn't wanted to agree, but the Ultra was so annoying that he eventually had no choice but to team up with the dumb couple and travel to different worlds to give concerts. The System wasn't only good at pestering Ultras, though. It could also help him get stronger. And he had to admit, the manager it provided was pretty great. Well, always calling him “sir,” and easily embarrassed, too. Ahem... Anyway, it's really not bad. That's all. As he completed more and more missions and transmigrated to more and more worlds, he discovered that he...