That is too vague a description to be sure what work you’re referring to. Care to expand or name it?
Had to go find it:
"Katainaka no Ossan, Kensei ni Naru ~Tada no Inaka no Kenjutsu Shihan Datta noni, Taisei Shita Deshi-tachi ga Ore wo Hottekurenai Ken~
From Old Country Bumpkin to Master Swordsman: My Hotshot Disciples are All Grown Up Now, and They Won't Leave Me Alone"
https://mangadex.org/title/0d4f9dba...kenjutsu-shihan-datta-noni-taisei-shita-deshi
Typical "trashy" title and the plot is... not that great, but the fight choreography is easily the best I've ever seen in manga. If you just want a quick sample:
https://mangadex.org/chapter/98bfd203-da15-4b85-b2a3-13601e22c429/5
Page 5 to 34. There's like... 5 lines of dialogue in that entire span, so if you ignore that you won't really get spoilers, and to help with a bit of the confusion, in their first encounter it was shown these two are so high level that they can see the "what ifs" and think moves ahead. So if you see an injury and it's not there later, that's why. It was a "predicted outcome, but was countered"