The only positive thing I can say about the series is the art: it looks rather good, and the artist can bring real intensity to the characters faces.
However, everything else is poor, to put it lightly.
The most notable flaw is how poorly the characters are written. The villanous characters are written in such a cartoonishly yet past psychopathic way that it's impossible to take them seriously. I can understand the violent bullying, but having suspension of belief for how absolutely off the hinge and one-dimensional all the 'evil' characters are is nearly impossible.
The Shigami, who put the MC in purgatory the first place, seems like the farthest thing from a redeemer. None of her actions feel like they have weight (to support or to counter him) nor that she's ttrying to help him redeem himself. Instead, she's just as stupidly written as the evil characters - constantly rushing him, doubting him, verbally abusing him like the bullies - it's almost like she wants him to give up immediately. But then why does she start the loop if she wanted to redeem him? And then why does she stop it if she wanted to continue torturing him? She's overall an antagonist without intent or weight. Just someone to kick the poor MC through the chapters.
And then there's hhis father being wilfully ignorant, nevermind how irrational he was in his miniarc. And then also the Chekhov's Toilet with the kid and Zach.
This is only the especially egregious.
Then there's the whole concept of "redeeming yourself after suicide, after watching how it hurts others". All it does is leave a sour taste in my mouth. It's hard to tell if this is from the author's inexperience in writing, or from ignorance about suicide, but the subject is tread on like the mc is simply going through a phase, and he needs to "learn from his mistake" and recover from it; which is a glorification at best. The suicide seems to be purely a plot element, rather than anything to observe and try to understand.
Then there's the supernatural elements
especially when he got REVIVED in front of everyone
, the nonsensical plot structure, the gaping plot holes of unexplained events and the almost decent but ultimately disappointing ending, but it's late and I'm about to ko. I'll see if I remember to finish this up sometime later.
TD;LR: Horrible handling of a suicide scenario, all characters are unlikable (except the dog), story execution was poor, art is alright.