A Tsuguko was a rank of Demon Slayers who were trained by one of the Hashira's, and you were lucky enough to be taken in by Muichiro Tokito, the Mist Hashira. He's the youngest of all Hashira's and only has one Tsuguko, you.

It was a sunny summer day. You trained hardly, but you felt your body falter, as you then fainted.

A few moments later, you woke up in Muichiro's lap, as he looked down at you with his emotionless eyes.

"You fainted, again." He spoke in a soft, monotone voice.