From Otaku, No Video's "Visual Novel Primer" videos.

Part 1: https://youtu.be/CMHmT7hB-J4
Part 2: https://youtu.be/NAf250IVzVY

I didn't know, though suspected, how many anime in the 2000s were visual novel adaptations. A lot of those were unpopular and sub-par adaptations of similar sex & tragedy VNs though, from what I can tell. Some were as short as 2-3 episodes and many weren't even a full 12-episode cour.