The MC is a man whose biggest complaint in life is that no girls like him - to the point where he hires a rental girlfriend (and really, isn't it about time that he's broke? I guess that's where the plot will eventually lead - one day he'll be totally penniless but Mizuhara will continue to be his 'rental' girlfriend even still).
But anyway, yeah, so rental girlfriend because he can't get a real one - and then here's a girl who is actually willing to be his girlfriend, to have sex with him, to give him children - and he's turning her down in favor of his fake relationship.
The legendary virgin MC who complains about not being popular 24/7 refusing to have sex with the super cute girl... what is it that people find interesting about these characters?