I Inherited a Last Letter and Punched Muzan Kibutsuji to Pieces!

[Demon Slayer + Akaza + Underdog's Rise] “Hey, Akaza, no, Hakuji, by the time you read this, I'll be dead...” “I'm you from a parallel world. You could think of me as a future version of you who's already dead. I'm the unlucky fool who failed to protect anything and lost his memories!” “I don't know what point in time you're living in now. If you're still human, there's still a chance to undo your regrets. Keep fighting.” I'm Hakuji. After my father died, I thought I'd spend the rest of my life drifting aimlessly. Then I met my mentor Keizo and Koyuki. They saved me. One night, I suddenly received a suicide note from my future self... That letter let me gain the abilities and experience of versions of myself who died on different timelines. Fulfill their last wishes, and I can gain the powers of different versions of myself, even stack their talents! I received help from countless versions of myself: Prizefighter Hakuji, Upper Rank Three Akaza, Hashira Hakuji, Twelve-Month Demon Akaza, Demonized Akaza, Soryu Dojo master Hakuji, vagrant Hakuji, murderer Hakuji... “What? That despicable kendo dojo next door poisoned the water at Soryu Dojo?” “Master and Koyuki were killed by them while I was away visiting my father's grave?” “No!” “Why is my happiness always cruelly snatched away just when I'm about to find it?” “I won't accept this!” “I won't allow it!” “I'll grow stronger, reach the summit, and become the strongest!” “I'll take control of my own fate!” “My countless selves in the future, lend me your strength! Together, let's reach the summit...”