But we do not know, maybe other G10 are in weak schools, or did not attend a tennis club back in their middle school.
Well, we do know some things about them:
- Byoudouin was in Makinofuji and personally I would guess they won the nationals three years ago. Makinofuji was regarded as a strong school going into this season, Byoudouin won the newcomer tournament two years ago and when he first faced Oni at the camp, he indicated that he hadn't been pushed during the school tournaments. So you had a great ace player and probably a good team otherwise to back him up.
- In contrast, Oni was apparently in a weaker school since Byoudouin didn't know him.
- Tanegashima and Irie both went to Maikozaka, who also made the nationals this year and might've been in a similar position to Makinofuji back then (though there's definitely less context hints).
- Ochi attended Hyoutei and lead them to the nationals during that year. You're correct that they didn't win Kanto, but regardless of which school Mouri attended at the time, it's very unlikely that he took out Ochi considering their results from this year's tournament.
- Duke and Tokugawa were both in France, so they definitely weren't a factor during the MS nationals.
Ohmagari, Kimijima and Tohno are ambiguous though.
With Ochi, I see him as a tough matchup for Ohmagari. If you go by stats, Ochi has 7, and Ohmagari at 3. I think that big gap of a difference in mental will be a huge advantage for Ochi. You could argue that Ohmagari has 7 stamina and Ochi has only 4. But it will not matter anymore if Ohmagari is already affected by Ochi mental pressure. I am not saying Ochi and Ohmagari should switch. But I think he have this what YOU called "Matchup advantage".
It depends on how the match goes, but it's possible for sure. The way I see it, Ochi's Mental is less of an advantage than e.g. Kimijima's against Ohmagari because of how these stats were determined. Here's why:
Ochi's Mental Assassin doesn't create pressure out of thin air, but amplifies pressure that already exists. This tends to be close to the end of a set or during big points. At the same time, Ohmagari's Mental description says that he has "absolute confidence in himself", which to me reads as if he wouldn't actually feel pressure when he's serving for the set or serving to stay in the set. This is arguably supported by him scoffing at Atobe in chapter 75 for double faulting during the decisive game of the opening set.
Essentially, Atobe (and Evangelos) had a mind set of "I have to hold serve", but I think in the same situation, Ohmagari would more likely think "I will hold serve" and treat it as a matter of course. So he wouldn't put any pressure on himself that Ochi could then amplify.
That's not to say Ohmagari will never feel pressure and never fall prey to Ochi's assassination. Ohmagari's Mental description goes on to say that he "looks down on lower-ranked opponents", so I would expect him to waver if Ochi managed to break Ohmagari's service game for example. And that's not impossible in my eyes, but it's not easy either. There's two points I would consider here:
- Ochi vs Heracles had the same dust clouds as Byoudouin vs Oni did and we haven't seen those appear in Ohmagari's, Kimijima's or Tohno's matches. It's not entirely clear what the dust clouds symbolize, but it was probably very high-level play.
- On the flip side, Ochi is a counter puncher, meaning most points he wins outside his service aces won't be quick, but drawn-out ones. You can see that in both the 9/10 match, where him and Mouri were mostly defending rather than finishing points fast, and the match against Greece where he ultimately drew an error off Heracles instead of hitting a winner. It'd probably be similar against Ohmagari because Nitouryuu gives Ohmagari quite good court coverage.
Because of the second point, Ohmagari's stamina lead might actually be a very significant factor even in the earlier stages of the match.
Looking at the match from the other side, Ochi also needs to be careful that he holds his service games. This shouldn't be a problem when he hits Mach at full power, but, as noted before, he can't do that in every one of his service games in singles. If he slows his serve down, I think Ohmagari can return it - he seems to be a good returner in general and once again indicated as much during the no. 9/10 match. Each time Ohmagari returns Mach, you're also probably looking at another drawn-out rally.
With all that said, if Ochi does manage to apply pressure to Ohmagari and then amplify it, I agree with you that he'll go on to win the match. In the end, the open question in my mind is how often Ochi can break Ohmagari's serve. Personally, I'm inclined to say it would happen in less than 50% of their matches, but others may see it differently.
I also want to briefly expand on what I said at the beginning, that Kimijima's 7 is more valuable than Ochi's against Ohmagari. The final bit of Ohmagari's Mental description that I haven't touched on yet says that he "tends to accept challenges and proposals from his opponents readily". Ochi would never take advantage of that because of how straight-laced he is, but it reads like great fodder for negotiations.
Kimijima will struggle even more on the physical side though. Unlike Ochi, who at least also has Speed going for him, Kimijima wins in none of the other stats. He ties Ohmagari in Speed, but is worse in Power, Technique, and of course Stamina. He essentially needs really great variety to outplay Ohmagari for two sets straight, which doesn't strike me as an easy task.
Is it because 1-5 have more promince in the story, and they likely have more powerups????
That's part of it, but not all. For 6-10, we know all their stats and I'm not expecting to see any new abilities from them for the rest of the series. Tohno is out of the picture, Kimijima and Mouri have already played and I'm inclined to say Ochi's match against Greece was his last one too. Ohmagari could potentially still play, but I think his role will be to train up Kite instead. In other words, we know quite a bit about all of them and are unlikely to see more.
It's different for the top 5. Byoudouin's and Oni's stats are hidden, and Byoudouin potentially has a move he didn't use in the no. 1 match. The boost Tokugawa gets from Asura is difficult to quantify. So even without considering that Byoudouin, Tanegashima and Tokugawa might still play another match, there's a lot more unknowns in this group.