Webthe hashira training arc introduced new dynamics, unresolved plot threads, and emotional stakes for future movies.
The arc left much unresolved, leading to.
Uzui retired as a hashira after his fight with gyutaro.
However, he still returns to train the others.
Webop clearly asked if zenitsu is hashira level and requirements for a hashira is either kill 50 demons or kill any of the moons.
And i've stated zenitsu is because zenitsu killed a pre.
To the hashira training shows the living hashira coming together to train the young demon slayers in order to prepare them for the final fight.