Wait do sexual abuse mean that the mc is being raped?
Simply put, yes.
This choice is about what happened to the MC while they were in the tower. It is your choice whether MC was sexually abused or not.
This is the least prominent in Ozara's route (one time touching at most), and the most thematic in Ruben's route. If you choose this option on Nour's and Ruben's routes, then yes, it means MC was raped while they were trapped in the tower.
Don't take this as criticism of the story, but as a lesbian player of the game, I personally would've loved for the 'scene' in question with Ozara to have been rape as well. I'm a survivor of rape myself, so I would've been really happy to have that part of my past represented, which makes it upsetting that, that particular route is cut off from that option entirely. Obviously it's down to League to decide, but I just don't understand why that particular route didn't feature rape, compared to the other two when the abuse is entirely optional regardless of what route you go down. Then why can't the female romance route feature it just the same? Don't think too seriously about it though, I only brought it up since I personally didn't think it made sense, so I would obviously not take offence if my request was denied at all. It was just a thought that struck me, when I learned about the differences between the routes in terms of the severity of the abuse. And sorry if my comment is a little incoherent, I'm kinda high at the moment, so it might not all make sense to those with a sober brain.
I'm guessing this has more to do with the Watchers. Raznith and Tyrae don't seem to particularly care what happens to the MC, as long as they're alive, so the guards are more likely to sexually abuse MC with the two Watchers fully aware that it's happening.
Fennore seems to try to appeal more to the MC emotionally, by gaslighting and treating them like a mother child relationship, so she'd probably stop any sort of attempt at rape, or at least dissuade it just to make it look like she's the only one who cares for MC. So, I'd guess that it's less likely that the guards would sexually abuse MC with Fennore around. At least, that's what I'm seeing based on the three Watcher's personalities. Basically, make it look like she's the only person in your world, and it'd be hard to do that if she just let's the guards rape the MC.