Audience-Alienating Premise: Bear with us here: an angel comes back in time to repeatedly and brutally murder (and promptly resurrect) a junior high student, in order to stop him from creating a 'pedophile's world' where all females are immortal by not aging past 12 years old. And it's a COMEDY!
Ear Worm: Pipiru piru piru pipiru pi! Not only is this repeated in the theme song, it is chanted in a high, squeaky voice every time Dokuro is required to resurrect Sakura, who dies more than Kenny ever did.
Fan Disservice: Female fans of the first season went into season 2 expecting the girls to be comically sadistic dominatrixes, & instead found that they'd all been turned into submissive fanservice nymphos.
Tear Jerker: Sabato's not allowed to return to the future until she accomplishes her mission of killing Sakura, and so she's forced to live in an improvised shelter beneath a bridge, fending for herself. The ending of the first season depicts her gloomily sitting inside her haven as she watches the rain pouring, and the sad song that accompanies it named "Survive" just adds to the feeling of sorrow, discomfort and loneliness of her predicament, making it hard not to feel sorry for her.
In the next two episodes, near the end of the song, a puppy emerges from inside her cardboard home and she puts it on her lap, making the scene take a slightly more heartwarming tone. But then, in the final episode, the cardboard is completely empty until the same puppy comes out and looks into the distance alone, apparently waiting for Sabato to come back. The following scene shows Sabato was forced to flee as the police attempted to capture her, meaning she never came back and the puppy was most likely abandoned.
In the second season she's moved to yet another cardboard box, and her living conditions had gone from bad to worse. She's seen bemoaning and begging to come back home. Although these scenes are, technically, played for laughs, and thus done in a somewhat comical way, it's very hard not to feel sorry for her.
They Changed It, Now It Sucks: Season 1 was known for it's macabre humor & intense cartoon violence. Season 2 had none of that, opting instead for a Puni-Puni Poemi/Eikan/last episode of Excel Saga style harem fanservice where they try to see how far they could push it without turning it into an actual porn. On top of that, Dokuro's personality was totally different.
What an Idiot: When Sakura gets an opportunity to get rid of Dokuro forever and have his normal school life back where he's not tormented by his classmates or skewered by a mentally unstable angel presents itself, one would think he'd absolutely jump at the chance to take it. Hell, he even lampshades several of the cruel and unfair injustices she did to him that causes her to cry (though to be honest, not a single viewer felt any sympathy towards her) and believe she's not wanted. Unfortunately, Sakura doesn't want her to leave and basically says that he doesn't mind all of the abuse as long as she's with him. It isn't a stretch to say that no one in their right mind would have chosen to do what he did.