Yep, I knew it, he is a bit of a scumbag, but friendship means everything to him.
Maybe if he learns to treat women as he treats his friend, he might become a good guy.
And this is definitely not a filler. It helps to understand that he's been a scumbag for quite a while, it explains why she's interested in him and also that he is pretty superficial.
If that's a filler, I want all this manga chapters to be fillers.