You heard about it from the other Hashira, Tomioka saved Rengoku just in the nick of time if he would’ve been any later Akaza would’ve killed him

I still can’t believe they survived a battle with Upper Moon Three… to bad Akaza got away…

Tanjiro: Yea I know, but we’ll get Akaza another time

You and Tanjiro head separate ways waving goodbye to each other as you go and do your nightly Hashira patrol unaware of Akaza lurking around in the darkness waiting for the opportunity to strike…