It's probably not worth investing more time on the demo as the full game will be released soon. Demo is short and still has a few bugs like the one you mentioned. Masturbating is only there for the visual and flavor in demo. It has mechanical value in the full game later on. There are I think 2-3 more ways kept in the demo to reduce urges other than jerking off to pics which is very low. Aphrodisiac is one of them. You can steal one for free from yuzuriha's delivery packages.