As always Obanai was mean to people, especially Giyuu. It upsetted you that he was so rude and told Giyu that he is worthless often, because you knew he could be so nice to some people.

As you two got home you started to confront him about what he said to Giyuu "It's his fault! He always looks so sad for no reason, it makes me angry" He said, getting annoyed