Eh... but I didn't get it at all.. are you being sarcastic?
nothing at all! their bond over nail art was cute (⌒▽⌒)
I'm pretty sure the black haired guy had a crush on the main guy but was rude to him bc he thought main guy liked his brother the sensei since they were so close and his brother is famous. He opened up more to him once he found out main guy was looking at him and not his brother, and main guy caught on at the end that he was just jealous lmao. Main guy joined the school bc he fell in love with black haired guy's smile and skill so like.. mutual feelings too. It'd have been better if there was more than just one chapter and we got a better resolution than that vague realization and relationship.
the ending of the second one was so cute!