In the time before Boku No Hero got serialised, there exsisted another with a similar premise of “the main character with no powers looking up to a hero of sorts and then gets a boarderline OP power before enlisting in an academy”….yeah that premise. This manga goes by the name of Black Clover.
In short imagine Boku No Hero with magic and more action (and better).
The OVA “should” be available to watch on all major streaming sites but you know how Crunchyroll tends to not have some stuff due to licencing and that.
So go check it out and come back and drop a comment here on what you thought about it.