datte mai no aniki mechakucha kakkoii jaa~~n ❤ だってマイの兄貴 メチャクチャカッコイイ じゃ～～ん❤ [That's because] Mai's older brother is super cool~~❤
kou ichi no toki bokushingu intaahai made itta tte 高一の時 ボクシングでＩＨ（インターハイ） までいったって During first year of high school [he] even went to the boxing inter-high.
nanka waruppoku nacchatta kedo なんか悪っぽく なっちゃったけど [He] became sorta bad but... (bad in the delinquent sense.)
soko ga mata ii tte musume ooi yoo そこがまたいいっ て娘おおいよォ Girls [who] think that part, too, is good are many.
i.e. many girls think him looking a like a delinquent makes him even more attractive.
chou iketeru yoo~~ 超イケてるよォ～ [He's] looking super good~~
