 If you liked
Gankutsuou
|
 ...then you might like
School Days
|
Both series star a naive teen main character who doesn't consider the consequences of their actions. Revenge is also a strong theme in both series. These shows are much more about the overall story than the characters - you might not be rooting for any of the characters because you find them unlikable, or maybe you're rooting for the bad guys, but the story as a whole gets you invested.