Otoha's Netorare Diary

The basic strategy is to gather information and funds through conversation. 

One goal is to use Hideo, Satsuki, and Milk to cuckold Otoha-sensei before her husband does, but as he meets and befriends a mob character, he awakens to the excitement of having him cuckold Otoha-sensei, and the main focus becomes getting her to cuckold him.

It is also possible to conquer Milk and Satsuki, and there are multiple endings, from a good ending that avoids NTR to a bad ending that results in NTR.