I Started a Club in Death Note!

He was hailed by the heroes of Rukongai as a great mentor, was a trusted assistant to Fourth Division Captain Retsu Unohana, and was even regarded as a kindred spirit by the slick-haired Aizen. That was how people once described him.

Aizen: “A Soul Reaper who doesn't use his brain will be a Soul Reaper for life. Nishikawado Motoka is different!”

Omaeda: “If I had to choose a Captain-Commander, I'd pick Motoka. He says he'll lead us in an assault on Las Noches!”

Retsu Unohana: “Motoka? His strong point is how fast he is!”

Nishikawado Motoka: “Ahem! Ahem! It's my sword that's fast!”

P.S. A Bleach fanfic, no System, slow-paced, starting over a hundred years before the original story and affecting its events.