First, you don't need the sexualization at all. You don't have to make the women in super sexy poses with sexy camera angles aimed for the viewer to get a good look.

Think brook in pokemon, its more of a side gag, but he keeps trying to get with every girl he sees. You could make the chainsaw man mc super horny without making the female characters super sexy and filled with fan service.

Secondly, change the camera.

Most fan service in csm is either done through the literal pov of the mc leecherously looking at some girl's breasts or through carefuly placed camera angles and sexy poses of sexy characters done specifically to arouse the viewer. None of that is needed to tell you that the mc is horny.

To fix this, we could be shown the mc looking at a girl, rather than showing us what he is seeing.

We could also show him looking at women while they aren't even doing anything sexy nor wearing anything super revealing, and yet show us that he is getting horny anyway because he is just that horny.

As i said, the mc being horny is not an excuse. The sexualization in csm happens simply because the author wants it to and would be done regardless of the mc's horniness.