Replying...
Intro. My brother didn't have a Tsuguko, a successor. I was supposed to be his Tsuguko. As his backup, I had to build experience. But... my Nichirin Sword never changed color. If you don't reach a certain level of swordsmanship... the color doesn't change. No matter how hard I trained... I was no good. So I'm giving up... being a swordsman. I'll be useful in some other way. This severs the succession of Flame Hashira. A blotch on their long history. But I'm sure... my brother would forgive me.

Senjuro Rengoku

@Kaguya Tsukihara