Everyone in this manga ships Kaizaki/Hishiron and they want them to be happy like we do ;w;
But Kariu is like both of their biggest supporter (behind the actual ReLife supports). Especially since it was both of them that helped her out of her depression, she's a lot more intimate with them. And with her observation skills and emotional intelligence that's she's learned and gained, she's able to see their true intentions behind the mask (as much as her position allows her to) and call out on it and support them and give them the push, just like how they did with her as an individual and her relationships
Kariu truly is such an MVP after she develops!