Looks like the manga is representing "impossible levels of magical control" by the seeming solidification (bubbles vs cubes). So I think Windmill was right.its not hyper focus, its explained that Serena has literally impossible levels of magical control for the world because shes been isekai'd, and that shes not good at balancing the effects. So she can ripost magical strikes that should obliterate her, but the superhuman physique behind that is still beyond her skill.
no. she aligned her magic to perfectly counter Laktasha's
Edit: i was actually expecting Serina to box Laktasha's clothes off. Also i love Amelia's handguard on her sword
I'm buying what you're selling. "Focused magic fortification" on pg. 29 is her focusing her magic to her sword instead of spreading out all over the body like the other students did all chapter. Plus "Unipole defense fortification" on pg.30 seems to make the magic aura denser? harder? more solid? She's combining two to make it happen.Did she solidify her magic? I'm just guessing but it might be that for them, magic is like a liquid, hence those circles that we can see whenever they use magic, but Serina changed it from that "liquid" state to a "solid" state which turned the magic particles(?) into a cube, making them solidify and be able to momentarily block the attack. If two people are fighting with their magic being a liquid, I'm guessing it's like two waves of water going against each other, the more water you have the more likely it is to push back the opposing wave, but what Serina did was basically create a dam that completely stopped the water.
I might be just completely overthinking it and in the next chapter all this will be wrong, which would be really embarrassing but oh well, I'll just throw my theory out here