So Rosario gets multiple clean hits on the head and is ok but Mashiba gets one and takes heavy damage? I don't mind the fights to be a bit exaggerated since it's a manga but then do it evenly on both sides.
1) Counters in this series are always huge damage
2) Mashiba's flicker doesn't deal much damage, it's a zoning tool
3) Mashiba's always had a glass jaw. Early in the series 1 or 2 hits to the face usually dropped him
4) Rosario's an infighter and brawler, he's used to getting hit and way more used to it than Mashiba
5) Rosario's not ok. On page 7, right before he lands the counter, he's barely able to stay up. He recovered a bit while Mashiba was down.
6) A clean hook to the jaw has a way easier time knocking someone out cold than a straight.