i dont think at any point in time we're supposed to reasonably want denji to actually want to be able to kiss these girls? even at this point, makima has all sorts of shade about her and is just using a kiss to manipulate denji into doing what she pleases, and himeno is a little predatory herself -- its not denjis fault for being 16 but rather the fault of the women around him for not promptly picking up on the red flags that denote hes younger (hypothetically this is csm so who really gives a shit) but part of the point is that these women are creepy for preying on denji and even moreso how even more vulnerable denji is to it because of his lack of any education and his desire for sexual love bc hes craving love and acceptance in any form.
this is made all the more tragic thematically by denjis age and his age contributes to how hes manipulated and creates the juxtaposition of his sometimes juvenile wants and concerns coupled with the fucked up world around him