Damn, Aimu, you're really falling for her in the shoujo Suspension Bridge way. But he is just so adorable about it that if it does play like a shoujo romcom, I can wait the 100+ chapters for it to pan out
Even if he isn't her "boyfriend", brother or anything it's still a man's duty to help a girl who's being harassed by a punk ass such as him.
Would you people just let it be if girl was attacked by asshole just because she isn't related to you. What sort of logic that guy use i still don't get it. Might be better that way.