I'm not sure about the specific favorability figures, but from the beginning, follow his desires, complete Gunnar and the merchant's house by expanding the village → Invite Gunnar to the fireworks if the option appears. Repeatedly visit when Gunnar and the merchant's house are completed. My memory is vague from here onwards, but there should be options such as cooking for him here and cleaning his body. I think I had the option to steal his underwear while he was washing. However, in the meantime, I tried to raise his favorability anyway. I also bought erotic novels from Northcrest and read them to him.