The Batman: Defender of Musutafu.

Izuku Midoriya accepted that he would be nothing more and nothing less like a normal guy. Just another civilian. Until one day, old Bruce Wayne came to Musutafu to demonstrate that he was helping and supporting a project that would put an end to the city's crimes, however, before the event could continue; villains and criminals attacked the place, in which Izuku was also there and was about to help Mister Wayne. And upon finding him, Izuku saw something surprising. Old Bruce Wayne was surrounded by criminals who were beaten by him, but what was actually more surprising than that... Is that he unintentionally ended up revealing what he is for the old vigilante who was known as... Batman.