I'm trying to remember a manga where the world are full of these cute characters.

It hints that the world for humans have gone to shit.

One of these characters found a human child and raises her.

The whole overall tone of the series is cutesy and wholesome with slight undertones of darker things.

One of them being a character who keeps her partner alive on a machine who desperately wants to die but nobody is aware of the fact that the partner wishes for death.