The Hero's Younger Brother Is a Deceased Person in the Academy

Story:

In the last battle with the king of the dragon race that killed countless humans, Rudd Denatos loses his comrades and biological brother, Aesir Denatos. The moment he slays an unidentified dragon that appears before him, he returns to his days as an academy cadet. This time, Rudd tries to kill all dragons, so the past doesn’t repeat itself. However, in the past, he has regressed into his brother, Aesir, a genius warrior doesn’t exist. Trying to fill in the empty spot of Aesir, Rudd tries to prepare as much as possible before the strongest dragon king, the Seventh Dragon, appears. Will Rudd be able to find his older brother and avenge his parents?