Yeah, that's a really bad down. That match really should have ended there and then. I can only assume that 8 count took like 30 seconds and the referee was stretching out the count with every fiber of his being to give Mashiba the time to recover.
I guess we shouldn't be too surprised that Mashiba ate that counter since he's always been a bit susceptible to head hunting, but I thought he'd have a convincing win against an opponent who isn't at their best. Instead he's getting concussed and making sure his sister still views boxing in a poor light.
It may have looked like a bad down, but that doesn't mean he can't get back up. A boxer can be back on his feet in less than a second once he recovers. He probably spent 4~5 seconds coming to his senses, ignore the montage. The ref is also not supposed to start the count until the other boxer has gone to a neutral corner. You literally see this in the chapter.
It also ultimately doesn't matter. The ref isn't required to count in seconds. The 10 count is just a 'technique' for the ref to determine if the boxer is able to continue. If he sees signs the boxer is recovering, he may slow the count to get a better assessment. Conversely if the boxer is clearly already recovered and is using the count to buy time, he may speed it up.
What matters is what happened in his head, not what it looked like when he hit the ground. That is just suggestive he had a serious concussion, but not a surefire indicator. It depends where exactly he was hit, how hard, what angle, how prepared he was for it. Heck, even how dehydrated is a factor.
Morikawa does not draw randomly (most of the time). The most probable concussions come when you hit the chin or front of the head, the back of the head, or when the head experiences snapback from whiplash. What we see is he likely took the counter on the side of his jaw, didn't spin much, and then he hit the mat flat on the side of his head. These are less likely to cause brain injury.
In any case, we don't need to speculate. He got back up and his eyes are alive, so clearly it wasn't as serious as it could have been. He was either lucky or prepared, or both. Makes no sense to cherrypick factors for a version of events that is already proven false.
Why would you expect him to pull an easy win anyway? In case you forgot, Rosario is a unified champion with two belts and considered by some the best lightweight boxer in the world. It's also not his first fight in 'bad' condition. It's still going to matter because Rosario is clearly now in worse condition than Mashiba is. Rosario is running empty after taking tons of body blows....go back to previous chapters and see how Morikawa has been consistently emphasizing the wind being knocked out of him. If you actually stop to think about it, outside of his downs, Mashiba hasn't taken much damage or tired out much. His obstacles are more technical, like the bleeding cut.
With that out of the way. Hey, I think this is the first time he's not only acknowledged Ippo's support, but it didn't come with any resentment
and he treated it like it was important to him. That's....quite a milestone actually.