Look at the spoiler about Rebecca in this post (for the reboot version): https://f95zone.to/threads/new-coral-city-v1-0-honeygames.28118/post-3375255I can't help you with the old version of the game but in the reboot version the MC has new personality traits. One of them is his respect towards women or the lack thereof. The latter will unlock an option where you can gift Rebecca a normal sized dildo from the sex shop which in turn will raise Rebecca's desire to have sex with you. I 'm sure there are many other ways to raise that stat but the other ones I remember are: telling her about your threesome with Luana & Yanmei and taking her to a trip down memory lane where you remind Rebecca about the titjob she gave you (you might want to offer her weed tho and literally make her more relaxed towards your sexual comment) hope this helps..
There are really two paths - relationship & sex (although you'll get both together obviously) and you get neither yet. For the relationship side there's a bug-fix in there. You only get to give her the dildo on the more sex focused path - as it's only mentioned after the dinner with Rain.