My Legend Lies Buried in the Past

The childhood sweetheart he once promised to spend his life with is a peerless genius. She's about to attend the kingdom's top academy, and a shining future awaits her. Ace, left behind in a rural town, becomes a laughingstock. But no one knows that all of Ace's awesomeness was buried in the past.

I'm not quite satisfied with the title. Another option is Time Arsonist. I'd love to hear your suggestions.