Without Superpowers, I Joined the Scriptwriting Group Through Sheer Intelligence

What Ranpo-sama says is absolutely right!

Overnight, Edogawa Ranpo returned to the past, fifteen years earlier. He saw a shrunken Dazai Osamu, Nakahara Chuuya who looked as if he'd never grown up at all, Mori Ougai before he got quite that interested in young boys, and the President before they had gone their separate ways. There was also a baby Atsushi Nakajima just learning to talk, and Akutagawa Ryunosuke looking well-behaved as he walked along with his little sister...

Edogawa Ranpo: ...This is starting to creep me out.

Edogawa Ranpo didn't know why only the great master detective had returned to the past by fifteen years. But there was a young Oda Sakunosuke right in front of him, Tsujimura Mizuki pregnant with a child, and Fitzgerald gently holding his lover's hand.

Edogawa Ranpo: ...No way.

He watched a procession of a yellow octopus, an ugly vengeful spirit, and a "knockoff little master detective" who kicked a ball in defiance of the laws of non-Newtonian physics while insisting that the world followed materialist principles.

Edogawa Ranpo wailed: This can't be real...

When Edogawa Ranpo, whose eyes could see through every truth, returned to the past by fifteen years...

Edogawa Ranpo: Why?! Why send a detective who can already understand everything back in time? A detective doesn't need to live with a script in hand!

Edogawa Ranpo, forced into the past, occasionally sent to the future, unwilling to deal with the plot, yet forced to join the script-writers: ...I want some dagashi.

Blurb two:

On the eve of the destruction of all worlds, a child made a wish, hoping someone would save the world that was about to be destroyed.

The child didn't know they had the ability to change the world. They used the one and only wish they'd ever get to have granted on Edogawa Ranpo. And then Edogawa Ranpo saved the world.

Change Oda Sakunosuke's inevitable death?

Change the ending where Byakuran destroys the world ten years later?

Change the fatal ending where a yellow octopus blows up the moon?

The hardworking master detective, forced to save the world: ...I'm done! I want to go back to my hometown for the New Year!

Theme: It's probably everyone getting together happily to make dumplings, haha