"Campbellian heroism", perhaps. Though strictly speaking a Campbellian hero doesn't have to be a conventional hero -- the Thousand Faces/Hero's Journey pattern is more about growing into your potential than about saving people or defeating a specific Big Bad -- and both seem to be indicated here.

As I think I've said before, the specific construction of heroism that MoR is using seems to inherit a lot from Fate/stay night, and more specifically from the "Fate" and parts of the "Unlimited Blade Works" routes. The concept we're pointing to usually gets translated there as "superhero" or "hero of justice", but I'm not sure what the Japanese is, and in any case I've no idea if Nasu was using a conventional phrase or if he's using a specialization of a more general word the same way we are.