Of the numerous unresolved plot lines brought about there is the vampire princess plot introduced in the second volume with our first real supporting character outside the protagonist's main family, Aiko the vampire. It is revealed when she drinks Yuichi's blood that she is different from other vampires and is actually a vampire princess according to the label over her head. New to her powers she is defeated by her brother a typical vampire that has been consistently drinking blood. However her transformation sets off a chain of events that starts drawing monsters from around the world to Japan because the monsters sensed her power. It is also revealed that she has 12 retainers from what is implied to be a previous incarnation, but only two of them are revealed with only one of them playing any kind of important role in the story and the other being revealed in the last few pages of the final volume. Needless to say this plot line is never resolved and is only used as a catalyst to help propel the story forward.

Our next unfinished plot line would be the Tomomi story arc that is hinted at bet purposefully ignored for comedy sake with Yuichi always refusing to hear out Tomomi's story when she tries to tell him. All we know about her plot is that for some reason her and her father, Nihao the China, run a restaurant in a sort of pocket dimension that normal people can't enter and that above Tomomi's head is the label fake. There is a Tomomi with a real label but she is only seen once for a gag trying to get Yuichi to ask about her circumstances. Beyond that we have no idea why the Tomomi we normally see is a fake, why her father has the label Nihao the China above his head and why this is also the name of their restaurant.
Next we have the Monika plot line. Basically Monika was ejected from her world view upon realizing that she was a world view holder and that made her an outsider. She gave Yuichi his soul reader ability kind of unwillingly after he saved her life and she tried to renege on her obligation to repay him. She wants soul reader back but Yuichi loses it and never gets it back himself. While this plot point is never resolved there is a more pressing plot point and that is that since she was ejected from her world view and she is no longer able to influence it, the world view has changed into something horrible. Her best friend from her world view holder days is now the love interest target of 12 serial killers and is in danger of losing her life. Yuichi promises to do something about it once he tries to bow out from the divine vessel war after finding out that reviving the evil god for a wish will result in the death of humanity. After Yuichi takes all of Monika's divine vessels for her own safety she is never mentioned again leaving us with no resolution to the plot of saving her friend, no resolution to her trying to get soul reader back, and no resolution to the debt she owes Yuichi as her initial offer was to give him her life savings of 360, 000, 000 yen or $3, 291, 733.25 at the time of writing this review, as well as her body via marriage before she wiped his memory thinking that would be enough to cheat her debt.
Now we move onto the backstory of one of a heroines Natsuki the serial killer. We are told that she is a "Jack the Ripper" and it is later revealed that the evil god implanted her with this Jack the Ripper to make her a serial killer. Her backstory is teased in the last couple of pages of the final volume with her remarking that it is a story of girl whose family was mu*dered, and who fell into the life of a serial killer. Beyond that the only other information we get is that she bought the Natsuki identity and it came with the house where she currently lives, implying that her stolen identity is that of a dead girls.
Finally we have the laundry list of crazy plot lines dropped in the closing part of the story to imply that though the series is over, Yuichi's life will never be normal. This includes mentioning that Tomomi is in danger of losing something called the Fakes Grand Prix, his seatmate is s**ked into an alien game of soccer to determine the fate of the Earth, the appearance of of the vampire princess's second retainer who immediately tries to kill Yuichi because he isn't "obedient" to the vampire princess, a implied future feud with between Chiharu and her childhood friend who is in love with her, Ende transferring into Yuichi's school presumably to keep watching his adventures as a fan of his, the yandere witch in his class looking for her target, Yuichi's friend from middle school, after he went missing, Yuichi being invited to the hero club with Yurika a real hero, Orihara's mother returning to Orihara's life and explaining that the mother is royalty from an isekai world that fled political strife and attempts on her life and now she needs Orihara's former power of isekai writer to return home, Yuichi being asked out by his middle school sisters "rival" who turns out to be an chicken anthromorph that wants to marry Yuichi to solidify her chance of winning an anthromorph succession war that the cat anthromorph Yuri is involved in, and then a reveal from Yuichi's sister that the world is facing a catastrophe that he needs to train his muscles, weapons skills, and electronic warfare skills in order to handle.