These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Arc Fatigue: For God's sake, you two, can't you find somebody worth a shit?!?
Hachi got pretty close to this with Nobu. Too bad the imbroglio about her pregnancy brought Takumi back into her life, some chapters after she loudly dismissed him over the phone after overhearing him complaining about how pregnant women are such a bother.
Let's say "everything sung by Anna Tsuchiya and Olivia" and leave it there.
Also, the insanely infectious "Glamorous Sky" from the movie.
Die for Our Ship: While Sachiko did get in between girlfriend and boyfriend, it still sucks that she's the one who gets almost all the shit, even though it was clearly Shoji who was two-timing with her and Hachi.
Ditto this for another couple in later chapters.
More so Reira in later chapters, who receives a lot of hate from both Takumi/Hachi shippers AND Nana/Ren shippers. Takumi, however, is still loved by fans even when he cheats on Hachi without a second thought, while his feelings towards her settle only slightly above indifference; and of course, Ren is the one who has been shown to have previous feelings for Reira, while Reira sees him more as a confidante and friend, and was clearly upset when the press threatened to release pictures that would persuade the public they were having an affair. Perhaps a milder version of Ron the Death Eater.
Idiot Plot: A lot of the drama stems from the two Nanas either making one questionable decision after the other or misunderstanding the other's intentions.