This is the most pretentious piece of fiction I've ever read.
Story: 1/10
What story!? There is none. We simply follow the main character with 1st world problems, not being happy with himself, with people around him, with the world, and constantly making dumb decisions that annoy the reader.
Characters: 2/10
The main character is 0/10, he is drawn as how a two and a half year old would draw a penguin with their left hand, so we can't properly see Punpun's emotions on his face, and on top of that he barely ever talks, which is clearly an attempt to make the readers insert themselves into the giant hole that the main character represents. All the other characters are between 1/10 & 3/10, and are just stereotypes, but on horse steroids. The only character who I found to be sort of okay was Seki, cause he seemed to be the only character that felt human.
Art: 2/10
The author did all that was possible to make the manga easy to draw. Drawing the main character & his entire family as a penguin doodle, but also copy-pasting the same panels again and again and again. When characters show emotions, it's almost always over the top unrealistic, as if the author wants to shove their emotions into our retina.
The worst part of this manga isn't the art, nor the characters, and not even the lack of a proper story, but the author's constant attempt to self-insert his own nihilistic philosophical opinions into EVERY SINGLE CHARACTER. This becomes obvious very early on, as the characters would suddenly start to spout out some philosophical soup full of rotten vegetables, while the other character that's listening to this doesn't have any argument back. And there was definitely a few times when the philosophical horse vomit that's been forcefully spilled onto our nostrils, was something that I agreed upon, but it doesn't change the fact that one of the most annoying things in fiction is when the author forces their own view of life onto their readers.
The only reason I didn't rate this 1/10 is because no matter how bad of a fiction I read, part of me believes that somewhere our there lingers an even worse piece of fiction, and that compared to that, even Oyasumi PunPun would taste like a high quality German beer compared to a bison piss.