The heroine can be turned into a willing slut, but only at the tail end of routes. For example, with the Banka corruption/NTR route, Umi is at first unwilling to show herself and what she's become to Umi. She begins to change, however, and by the end of the route is enthusiastically flaunting her debauchery. For the most part, outside of those kind of end-route events, the NTR involves coercion or implied coercion.
There is mind control, but it's not the way the heroine is broken. Mind control is used to control the other villagers, and is used to threaten Umi into compliance by forcing the other villagers to put knives to their throats. Another threat is that if she doesn't go along with what Sifu the Wizard wants, Kuru her husband will be murdered by a mind controlled villager in his sleep and her house will be burnt down. In terms of the heroine herself, however, she isn't mind controlled into compliance, but mind control is used to soften her up. For example, she's got a compulsion where every time Banka gropes her or whatnot, she likes it a bit more, hence the corruption ticking up. During battle, if she gets too hot and bothered, she slips into a trance state, which is when Banka helps himself to her pussy. Apart from that, she's fully in control of her mind and body.