They’ve basically all already fallen, but Terena is the only official one so far. She had already decided that she enjoyed cheating on the protag more than being with him back with the clothing room sex scene, where she declared the kid her real lover, but he told her not to break up with protag so that she can cheat on him more.
Reitta’s affection chart already has the protag lower than the old guy, and her latest event with the kid, the kid “corrupts” her by making her cheat on the old guy, and admitting his cock is better than the old guy’s. With the narration even noting “she apologizes to the head priest, like it was natural, and doesn’t even think of Kurt”. I wonder if her official fall event will be something like having the old guy decide she’s just a cum dumpster now, and make her have sex with a bunch of guys in front of protag. People in this thread have noted that these two had it pretty rough and were corrupted a lot faster than Arika for various reasons. So at this point their NTR scenes are less about them succumbing, that happened ages ago, and more about the protag getting off on being cucked.
And Arika’s next event will be her officially fully succumbing, but she’s already been getting off from cheating on the protag as early as the maid sex event in the bathroom, so there ain’t much left there. The narration even started noting that while the protag is telling her to run and not deal with the old dudes sexual orders, that she doesn’t seem upset by her circumstances at all. The next event will just be finally making her womb tattoo fully glow with love for the lord, and her getting pregnant with his kid. The whole thing with the tattoo being it will only let the person she deeply loves the most get her pregnant, and that it fully glows during sex, only when that’s about to happen.