I'm a person who rarely gets involved with people outside my school and family. Talking to people on the internet is also a worrries me, but as long as you promise not to kill me then sure. I look forward to debating/communicating with you. Also still getting use to texting so please dont mind my typos. Or my my southern American dialect.
protip for that internet anxiety: Never, under any circunstances, put real info (data, pictures displaying faces or recognisable places, etc) about you or your family in a conversation or a post in internet. Easy enough, no bad people will ever reach you ;)
At least from internet.
I think it was when he was unable to heal himself and she just keep firing magic at him. She might not have meant to kill him, but if it continued he would have died. She was irresponsible and reckless. It doesn’t mattered if she cared/ tired to help. She caused him harm, turtored him, and isolated him. Don’t forget she basically tried to enslave him. It doesn’t matter if he was leaving her, everyone has the right to choose who they want to be around. He didn’t want to be around her so he shouldn’t be obligated to. Everyone needs time to sort things out, and process things. He needed time to grow and heal himself, but what she did was filled his time with more pain and suffrage. I believe she cares about him a lot but understand she and him are still children.
I don't doubt that if Mina's pushing kept going he was bound to break at some point, but she's smart enough to control her strength as to not kill someone that's kinda her friend. It was shown that her status and talent isn't just appearances. She's pushy and beligerent but she's no psycho.
About Nack, that's one way to see it. As I see it, it wasn't that he didn't want to have Mina around, more like he didn't want *anybody* around, he was taking their discrimination about healers and started to alienate himself too, and it's evident it was less to think things through and more to submerge the situation, walk the other way and ignore it while lamenting. Thus resulting in his magic growing an emotional lockup that didn't let him heal himself. which changed when he swapped to a protective attitude towards people.
His situation wasn't an easy one to accept, at all. but instead of doing something, *anything* about it, like for example: complain, retort and/or rant about his disowning on his parents faces, you know, as a child would, instead he just resigned, and decided to avoid everything even if it was someone trying to help him, as it was with his little sister, at the start with Mina and at the start with Usato (The latter was just more pushy and convincing than him stubborn).
You know what I'm thinking about right now? it's crazy, but this thing has so many elements similar to the start of Boku no Hero Academy. Like Kacchan as Mina, the beligerent runt with talent and big ego that sees Deku/Nack as his pathetic but necessary and overly abusable underling, with the difference that instead of a Deku, we got ourselves a quasi-Shinji Ikari xD Then we got Allmight/Usato to tell him that it's possible for him to be a hero and train him. Crazy, I know xD
Okay, personally.
Mina did get on my nerves at first but now I can't seem to hate her because I really dislike Nack's past self since he's timid, spineless, and runs away. It's kind of his fault so I don't blame her for acting that way. I hope the next chapter clarifies their relationship.