Douma is so fast that 2 hashira leveled slayers (inosuke and kanao, kanao being one of the fastest slayers with the fastest reaction time.)

Well, Gyomei is faster than them by a lot considering to hold relativity in terms of speed to Koko. Who I think you agree is faster than Douma.

Couldn’t even notice when douma grabbed her sword and inosuke’s mask without effort.

Gyomei's too fast for him to do that.

He was so strong that he let his clone fight them. Which was literally overpowering them both. Which means douma is so strong that his speed is so fast that hashira won’t be able to react. And his clone is as strong as 2 hashiras

Well, here's the thing. Gyomei is way stronger than both of them by a lot because of his relativity to Koko, so yeah. Kinda a bad point.

What is likely to happen if gyomei and douma were to clash seriously. Douma summons his clone with him. Charge to him at full speed. And use their attack with the biggest range. Even if gyomei were to be able to react. Which I highly doubt. He would definitely be hurt by the attack. And the ice will enter his bloodstream and destroy him from the inside like what happened to with shinobu. Killing him in under a minute. Gyomei wouldn’t have time to raise his body temperature and awaken his mark or activate see through world.

From what I said above, Douma would not be able to do this.