Yongsa Dongsaengeun Academy Goinmul

A younger brother named Ruud Denatos loses his older sibling, Aesir, a gifted dragon slayer, after a deadly confrontation. Following the battle, a concealed dragon lord transports Ruud to an alternate past where Aesir never existed. Seeking answers and a way to reunite with his brother, Ruud assumes Aesir's identity and gains recognition at the academy for his abilities and knowledge. However, concerns arise about whether Ruud can maintain his impressive performance or if his previously unremarkable skills will eventually hinder him.