There is zero chance that the relationship with Moka will work out, they just don't seem all that into each other.
This is the japanese way of being into each other. Moka wrote him a confessional letter, she's been thinking about him a lot. And Ueno-kun has been into her since the beginning. And after what I expect Ueno is going to admit to Moka his sexual perversions (probably without going into detail of the three girls who regularly had his way with him), I think she will accept them and try to work it out.
While there is some special tension between Ueno and Chisaki, it's really Chisaki who has been developing feelings for Ueno, not the other way around. Ueno only has a sexual weakness for her, that's all.
And I forsee the dynamic being Chisaki trying to interfere as Moka and Ueno start dating.