Non-romantic sad anime recommendations

Some anime rely solely on "shock-sad" effect like killing off a character to make viewers sad. I think it's a shallow trick and gets pretty ineffective after a time (Akame ga Kill is a case in point).

The other category is the sad-ending/bitter-ending romance (I want to eat your pancreas, plastic memories, Hotarubi no Mori e, etc.)

A sad anime should go beyond romance or shocks to evoke the sad vibe by creating a sad environment through plot, sound and pacing.

An ideal sad anime should be a slow-placed where there is a perpetual sad vibe. It need not make you bawl your eyes out.

Examples: Sonny Boy, Dororo, Elfen Lied, Scum's Wish, Steins;Gate, Welcome to the N.H.K., Death Parade, Erased, Flowers of Evil, Haibane Renmei