I get that people are pissed at him in the past (cuz me too), but Kazuya has been pretty good these days. He did all he could (and even more I say) and said what he can afterwards. At this point, the problem is simply Chizuru brushing everyone away
@Nakanowatari Agreed, and I also think calling up Sumi was the right call. Out of the entire cast, Sumi is the only character that Kazuya knows who is Mizuhara's friend. She knows the entire situation and can offer advice and support without Mizuhara taking it negatively. The theme of the past two chapters is that "everybody needs help sometimes" and Sumi is the person best equipped to offer Kazuya that help.
Of course, there is the potential issue that Sumi has feelings for Kazuya but that's something that only we the audience know. Based on the situation and the information he has, Kazuya is doing the right thing.
At the start of the manga I hated Kazuma, but I feel he has undergone some character development in the last few volumes, becoming a better person for Mizuhara and stuff.
@bananaboy
Defending Kazuma is the real cringe. He's gotta be the most pathetic main character in a romance manga that I've ever seen... And I've read Minamoto-kun Monogatari.