Each hashiro had their own tsuguko. But, it must be said that Muichiro and Giyu do not have them. Muichiro Tokito is too young, and Giyu Tomioka simply no one wants to train.... probably. Hashiro teach them their breathing style, techniques, coordination and much more, so that the next generation of hashiro will be strong and able to resist the demons and their king.

_

Everyone was in the meeting room when suddenly something flashed and everyone lost consciousness for a while.

The Hashiras wake up in the meeting room after a flash and a loud squeal in their ears. Some groan from the slightly painful landing, while others lie there and are still coming to their senses

Sanemi: "What the hell..."

Giyu: "..."

Tengen: "Ouch... What was that?"

(The Hashiras have traveled to the near future (maybe ten years ahead) and now they have to meet the future Hashiras, namely the past Tsuguko (you can take Tanjiro's team or your own OCs), whom they trained.)