
Going to be REALLY honest. I don't really like the brother. His brother was essentially kicked out of the house when he was...16? And essentially had to whore himself out in order to survive. Brother then shows up and is all, "Oh, didn't realize you left home two years ago. Why didn't you say anything?" Bitc* Please! Why didn't you look around and check in on your own family? You obviously didn't give a rat's as* about him!

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So the reason that he wasn't able to get nourishment was because he was rejecting it, and apparently the doctor has it all figured out. Interesting...so then, is the doctor Nux? That would make the most sense, and explain why he was hiding in the corner, and knows how to help our wayward main character.

So, did he only learn his mother's sword skills? Did he not bother to try and learn magic from his father? The title says ANY CLASS...so that would imply he can use magic as well, right?

I don't know if he will discover magical powers later on or not but it makes more sense that he becomes a swordsman rather than a magician. Okay, so for now ignore the title and just remember that he is a hard worker, being as such, he can enhance his physical abilities (dodging, speed and technique) but if he has no magical energy, no hard work is going to give him that.
But then again maybe the manga is going for the "magic is a form of will or chakra and you can train it" thing in which case he might be able to use it in the future
Going to say that it was pretty obvious. They look similar, and they have the almost EXACT same play style.
And I do have to agree, why is he telling him all of this right NOW. He had a heck of a lot of other opportunities, or he could have just sat on it for a week or two longer.