I consider CLANNAD to be more heartwarming, than depressing
I just finished Welcome to the NHK.
I have a lifelong friend who is a hikikimori. The most depressing part about watching this for me was knowing what will inevitably happen one day.
His father will die. He will run out of money. With empty cupboards and an eviction notice on his door he will beg me for help(not looking forward to this conversation). He will then be faced with the choice of supporting himself or dying homeless.
I actually found the first few eps of FLCL depressing, even with the fun animation and music the problems and setting the characters lived in were pretty real.
Let's ignore the huge iron shaped factory and horns/robots growing out of people's heads.