Blood+ is sad but if you want to shed tears of sadness watch Grave of the Fireflies.
Basically, it takes place in WWII and these kids mom dies by getting blown up by an
air raid and their father dies in the war. The boy is like 9 or 10 and the sister is
like 6 and the two have to survive on their own. They live at their aunts house for a
bit but she's a bitch so they run away. They capture a bunch of fireflies and they
are symbolized throughout the entire movie. The sister is dying from malnutrition and
the brother has to steal food to keep them fed but he gets beaten. Then you see
fireflies dying and they end up making graves for them. Then the sister ends up dying
and in the end, the boy dies. And throughout the whole movie, I'm crying my eyes out
because you learn to love the two children.