I know those 2, but I don't think they are underground. Most people seem to know Kare First Love, but i'm not too sure about Ayashi no Ceres. I believe Bitter Virgin is better than Kare First Love, but thats just my opinion.

Heres another one people don't seem to know about. There is a manga version of this series, but the anime came first so its best to go with the anime (Unless you want to play the AO-rated game in Japan which started it all). School Days is yet another romance manga, but this time it focuses heavily on angst. It really does get you pissed about how the main character treats the other main characters, but for some off reason, I enjoyed this anime for its drama. I seriously do hate the main character though. School Days is basically about a love triangle that happens between 3 students in high school. 2 girls go after one guy basically. I'm not too sure if others would enjoy this anime mainly because of its angst drama. I myself don't truly know why I enjoyed it, but maybe you should give it a try. I guess I could call this an underground jem, but I bet others might think it is. Just give it a try and maybe you will like it.

http://www.youtube.com/view_play_list?p=7E061D9A515DC7E2

Heres pros and cons.

Pros: One of the most twisted angst, drama story that has yet to be treaded on; Mature-themed storyline of teenage love/betrayal; Character development is well paced; Art direction is simple yet fits the anime well; Animation is smooth; Music is quite good (Especially Kanashimi No Mukou He); Teaches a lesson about life; GREAT ENDING (IMO).

Cons: One of the most twisted angst, drama story that has yet to be treaded on; Due to the extreme amount of angst found in the anime, the anime won't win everyone; You won't appreciate the anime enough until you watch it all; Only 12 episodes.