We can't forget that part of the relationship can we. 
Yes it is possible, through Arianna questline, basically you need to get to the heart of the daughter to get to heart of the mother
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You can take women from other men (true for well over half of the female characters in the game), you can use dialogue to willingly let other men have sex with your women (just under half the female characters have at least one such scene, some have more than one, Kate notably has about a dozen), you can take or not take certain actions so that your women 'betray' you and sleep with other men without your explicit go-ahead (over half the female characters), and you can 'fail' a combat encounter resulting in your women being raped (I think about 5 female characters have at least one such scene, though only your two potential party members have multiple of these). It's actually easier to count the women who appear in-game that have no NTR content at all (9 by my count, and 4 are basically non-characters with no content yet, while 3 have NTR routes planned out).
Ah, thanks for the reply! I'm a huge fan of consensual NTR so I'm happy to hear that us as the MC can initiate it, not so much a fan of NTR beyond my control though so I guess I'll have to be careful to avoid those scenes.
The NTR scenes without the MC's consent tend to be either time-based, money-based, or decision-based regardless. For example, the mayor's son can use your personal aphrodisiac to make some girls more receptive to his advantages, but he can't get his hands on the stuff unless you sell it to the store in the first place. And even then, you have the option of switching out the drugged wine with some normal wine. Regardless, just use the walkthrough if you're nervous. It's fully up-to-date and clearly spells out the different routes and consequences.
Challenging Dasan after losing to him is planned in future updates
GOD
You can pick it up by interacting with any hay, the closest is the hay right next to Penny's house
