Doing some research on this matter, I found some decent options for those who are young. I found things like TOON, Hero Kids (which it looks very similar to the ruleset you used in The Story Game, despite being informal), Tales of Equestria (for My Little Pony fans, that's a thing), Beyond the Wall (basically, old-school D&D with a step-by-step process of creating settings, characters and scenarios), Chief Engineer... and many more.
While I started on 5E, I went for BFRPG because WOTC messed up D&D after the 5.1 SRD was made Creative Commons, which completely goofed with the OGL.
