Base-Breaking Character: Yukina is written with a really inconsistent personality and can go from a confidant, dominant girl to a shy, vulnerable mess at the drop of a hat. This greatly confuses readers, especially ones who had been attracted to her strong personality. Yukina's tendency to switch from Akira and Shigure without considering their feelings also generally makes her unlikeable. However, there are some readers who are quick to overlook these flaws and vouch for her as a strong female lead.
Draco in Leather Pants: Hisame. Hisame. Hisame. Fans are willingly to excuse Hisame's actions due to said Freudian Excuse and go so far condemn Mami for rejecting him despite the abuses she suffered from him.
Jerkass Has a Point: Hisame might be a Jerkass of the levels one would think he wishes to reach the likes of Makoto, but he did have a point when he called Yukina out on her Master of the Mixed Message below. Although unlike Hisame, who toys with other people's feeling on purpose, and laughs about it, Yukina at least has the excuse of being clueless about love and self-unaware about the feelings of those around her.
Later on Hisame also pointed out how it was pretty cruel of her to use his and Shigure's lives and private family problems for her novel. While she hadn't really thought about the consequences of her actions before, he's not wrong to say you should at least ask the person first.
Moral Event Horizon: Hisame, Shigure's brother, was introduced as Jerk with a Heart of Jerk, who likes to spite Mami for his personal amusement, and his brother out of jealousy. But once he reveals that Mami's hairpin, which was her deceased mother's keepsake, wasn't hers, and that he was the one who gave her the hairpin and made up that it was her mother's, doing so only as a way to have Mami wrapped around his little finger, he's collecting deathwishes from most of the series' readers.
If that wasn't enough, his blackmail of Yukina definitely made him the most hated character in the series.
Take That, Scrappy!: As of Chapter 61, Hisame gets rejected by Mami HARDCORE, to the point that she wont love him for her entire life time. Hisame then runs to Yukina to be comforted, only to hear that Shigure is her number one,thus leading to a dual-whammy ending up with shutting himself in with only his novel left to cling on to.
Hisame easily tops both of them. While Akira or Mami have at least some redeeming features outside of their involvement in Shigure and Yukina's relationship, Hisame has none, and each chapter he shows up he tops himself in his almighty jerkassery. Not even his Freudian Excuse of always being preferred over Shigure is enough to redeem him for most readers.
Yukina becomes this in later arcs (see above Seasonal Rot for reasons).