It's horror so of course it's going to be dark, but it's sad too. A curse causes the death of many students before paranoia and hysteria take out most of the ones left. I wouldn't say it brings tears to your eyes, but I find the concept rather sad.

How many sad death scenes are in this anime? A LOT. That alone puts this anime on the list. I don't think I ever came close to crying, but the subject matter is pretty dark.

Overall, I wouldn't call this anime depressing. So why is it on this list? It's here mainly because of two scenes. Children dying is sad on it's own, but children who know they will never live to be adults and are forced to fight and often times aren't even treated like human beings is worse. I won't spoil it by telling you the two scenes I spoke of, but I will say it broke my heart.

Children are forced to play a game, after being tricked into a supernatural contract, to weed out the various earths in existance. The rules are simple but terrifying. Each child must take a turn piloting a giant robot and fight against another robot. If they lose, the whole earth is erased from existance. If they win, they die imedeately after the battle. To add to their problems, it seems their life and relationships are somehow pushed into a fragile state right before it's their turn. Meanwhile, the government hides the truth from the people and offers little help for the children. There are only two ways to escape the contract; die or be the last one chosen to pilot. The world is quite litterally in the hands of these children. Overall, it's pretty damn depressing. There are parts of the plot that could be better, but it's still psychologically effective.

Depressing. I rarely actually cry while watching something but I was sobbing. It might have partially been due to the recent experiences I had in real life not long before I watched this, but it's just depressing. DEPRESSING!!

To prevent the death of his mother, the mc must return to his childhood and find a way to keep one of his elementary school classmates from being killed. It's something only he can do since he is the only one with the ability to go back in time (although he has no control over this ability). 

Personally, I think the original anime is far more emotional than the brotherhood version. The brotherhood version follows the manga more, but it didn't get my emotions as riled up. The beginning of both though was what really put this one on the list. The original beginning had a lot more emotional impact. I just wanted to hug the boys tightly. I was emotionally invested within the first few episodes. The brotherhood version left me feeling rather emotionless towards the characters at the beginning. It's practically the same plot in those episodes, but the way it was presented just wasn't as good. Also, the ending for this one was very depressing to me. I hated it because it wasn't what I wanted to happen. I wanted them to finally be happy together and all that fun stuff but nope... :'(

This one may seem like an odd addition to the list, but in truth, I found it pretty sad. The mc only knows how to solve problems one way. He makes himself the target of everyones anger and hate. While it gets the job done most times, it hurts those who see it and care about him. In a way, he is self-destructing. On the surface the anime doesn't seem dark at all. The title includes the phrase romantic comedy...but I would say it's a dark romantic comedy.