[I don't own My Hero Academia or anything to do with it all rights to to their respective owners. I also do not own any content that may be of other owners e.g. Percy Jackson]
Izuku Midoriya was a exceptional child, his intelligence at a young age was incredible, his joy everything about him was interesting, but one thing drew the attention of somebody big. His heroic will. He was a natural born Hero, yet he was the weakest in this world of Quirks.
Perseus 'Percy' Jackson, was a hero from 300 years ago, a demigod son of Poseidon turned God, he had defeated rouge Gods, Titans, Giants and even primordial Deities, specifically 4 primordial Deities, Gaea, Tartarus, Nyx and Erebus, the strongest deities in the world. After betrayal by the demigods the Gods immortalised their ultimate Hero, joining their council as the 15th Olympian, and that's how it stayed.
Until the incident...
(I will try to keep everything like how it is in the anime and books but it may be difficult, like after 300 years Percy had to of taken some personalities to the Gods so please understand if he's more arrogant and the like. He's spent to much time with his uncle Zeus...)