I know Kazuya's character is literally all about wanting to please Chizuru, but it's still ridiculous how that affects the investigation bullshit.
The dude wants Chizuru points because he thinks this whole arrangement is some sort of final exam with a passing score. This couldn't be further than natural. Under the same roof with the girl he confessed to not only once, but somehow I should think his lapdog behavior is admirable, selfless, and he expects nothing back
He lives everyday in fear that even a grammatical error in a sentence means he is going to fail the investigation. There is barely if anything to oversell about him, but he manages to be a tryhard knowing the (fake) stakes.