After finally destroying the Dark Lord, the Slayer and his brother Y/N is give 2 choices. The Slayer will rest forever in a coffin for 10 centuries or Y/N must go into the Azur Lane universe to repay for their penance. Choosing the 2nd option, Y/N bids his older brother farewell as he enter a new universe. 10 years later, Y/N is now the Commander of Eagle Union and META forces. But when the forces of Hell is summoned by the Sirens, the brother of the Slayer must face his past once again.