* The end of episode 20 of the anime is especially sad. Pudding is sick through the entire episode and after getting better and taking care of the house and her siblings thanks to her sister's teacher she ask the teacher for a favor. She ask if could pretend to be her mother, who passed away years ago, for a moment and she agrees, Pudding then begins to cry and you can tell that was the first time she cried in a long time.
* If you think about it, the aliens. Somewhere, there is a *planet* full of people who are forced to live underground due to the cold and instability of the surface. As if that wasn't enough, a message from their home shows what seems to be an earthquake. Those people are dying from starvation, cold and probably diseases. It's no wonder they are so furious about how humans are destroying Earth.
* Although the show doesn't go into details, Zakuro's life has undertones of this. For some reason, she cut ties with her entire family and apparently, the only person she loved died (and it's implied, though never said, that rumors and doubts led them to distrust one another, which may be the reason he died in the first place. We never learn if this was her friend, her father or even her lover). This girl is only fifteen.
** The letter she receives from home also states that they don't know if she ever forgave them for something. What if her family was behind said rumors?