This is a manga for people who are interested in slow-burn, character-driven psychological horror.
It also may be cathartic for people who experienced psychological abuse, or at least who empathize with those with psychological disorders (but, note, it may be triggering for some). For those of us who, in real life, have interacted with those with borderline personality disorder (BPD), this may be the most accurate depiction and emotional expression of both someone having that disorder, and the damage it can cause to those around them.
All of the main characters are three-dimensionally developed, have individual, believable motivations, and interact in mostly realistic ways. When the actions take a turn and become almost unrealistically cruel (e.g., the van scene), most readers don't understand that this is the wish-fulfillment playing out of some of the urges someone with those disorders have, exacerbated by it occurring in a child (who can't regulate those emotions well already). These then play out in a way that is believable, showing the long-term psychological effects of impulsive retaliation.
This is NOT a typical dopamine-loop seinen manga, or a generic horror manga. The 1s in this thread seem to be from people who don't get the manga, haven't had the experiences to understand why this is realistic, or are impatient with "side" storylines that are actually the point of tracing the effects of the main character's actions - like following the cracks after viciously chiseling a stone. That's ok, not everyone is the right audience for everything. But if the above description is interesting, don't let the 1s dissuade you.