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.
Alternative Character Interpretation: Is Shiro really who he says he is, or is he as evil as the snuff film suggests? The former is by default more likely due to how consistently not-evil Shiro seems to be, but he has proven to be a great actor and good at improvising. This, coupled with his distinctive manner of speech (he constantly projects a happy persona even when he's feeling down, which makes him sound insincere at many points) and his lack of seriousness could be interpreted as signs of him hiding something dark. Notably, Kuroh keeps the latter interpretation in mind as he "evaluates" Shiro. On the other hand, the few times we see Shiro while no one else is looking, he still acts like his goofy, compassionate self.
It's neither. Shiro isn't who he says he is, or even who he thinks he is, and he also wasn't the one to kill Totsuka. His true identity is Adolf K. Weismann, the Silver King. The one who killed Totsuka was the Colorless King, just like the video claimed—just that the Colorless King is a being who snatches the bodies of others and eventually absorbs their personalities. After killing Totsuka, he met with Weismann using the excuse of introducing himself to him, only to attempt to rob him of his body and his powers. Though the Silver King's own abilities protected his soul and his powers from the Colorless King, he still got body-snatched. His errant soul thus went into the nearest body available—the one the Colorless King had just left, the one who we would come to know as "Yashiro Isana". The shock and strain put on Weismann from this event gave him amnesia, just perfect for the Colorless King, now in Weismann's body, to drop him from his own airship and frame him for his murder. Shiro's personality is actually just like how the young Weismann used to be, before World War II happened and his sister was killed.
Complete Monster: The Colorless King in all spades. For starters, he took control of a young teenager boy and shot Tatara Totsuka (the only pacifistic member of HOMRA and a Nice Guy at heart) to death, thus escalating the conflict between HOMRA and Scepter 4. He later meet up with Adolf K. Weismann, the Silver King, under the young boy's body and managed to Body Swap with Weissman, thus effectively framing Adolf K. Weismann for the murder of Tatara Totsuka with amnesia. When he was a dancing with a masked lifeless woman (heavily implied to be one of the victims that he possessed) in Weismamn's blimp, he decided to "celebrate" his Scepter 4 "guests" by blowing up the blimp, thus killing the said women and nearly killed Yashiro in a helicopter, but left Adolf K Weissman's body unscathed due to his immortality. He then later possesses a random highschool boy and calls Mikoto Suoh through the phone by admitting to kill Tatara Totsuka and threatening to hurt the other clansmen next (including raping Anna, who has no ways of defending herself) simply to get a reaction from Mikoto. During the fight between HOMRA and Scepter 4 at Ashinaka High School, he possesses a random Scepter 4 sniper and tries to kill Anna. And during the said fight, he even managed to possess Kukuri, a cute highschool girl, and puts her in even further harm. Why did he all of this? He wants to be the only king in the world through Body Swap possession and create as much chaos as possible. In a series where neither HOMRA nor Scepter 4 are portrayed good and evil and very complex and moral ambiguous characters, the Colorless King is pretty much the most despicable villain ever.
Hidaka in Days of Blue Chapter 1 seems to kind of view Fushimi in a similar light, but thinks Fushimi just has a Jerk Ass Facade. He thinks Fushimi wants to open up to everyone and invites him to their party. To nobody's surprise Fushimi cruely rejects Hidaka's offer.
Fan-Preferred Couple: Though there are some other popular shippings, it's clear that the Saruhiko/Misaki pairing gets more attention from fangirls.
Foe Yay: Quite a lot scattered throughout the anime.
Most notably Reisi and Mikoto, who are enemies but seem to care for each other to a certain point.
Yashiro and Kuroh can also be considered such, at least for Episodes 3 and before, where the latter was persistently trying to kill the former.
Definitely some between Fushimi and Yata, as Fushimi was practically stalking Yata in episode 3. He is also the only person to call Yata by his first name, "Misaki". In Episode 5, he wasn't just a stalker—he was utterly crazy over Misaki in a creepily sadistic manner reminiscent of a Yandere, enjoyed seeing him cringe and purposely presses his Berserk Button, complete with a Slasher Smile and Psychotic Smirk, and he positively flips out at anyone who tries to get between them.
Yashiro is not so shy about blushing around Kuroh, even to his face (as seen in Episode 3 when he shyly asks if he could call Kuroh by his first name. And then in Episode 4, Yashiro jokingly calls Kuroh his wife.
Kuroh is unbelievably blushy when discussing his late master Ichigen.
Between Suoh and Munakata. When discussing the ticking Time Bomb-status Suoh's powers are rapidly climbing to, Suoh proposes that one way Munakata can keep on eye on that if killing is not an option is to keep him company 24/7. In a cell. Hell, the entire conversation exudes Ho Yay subtext!. Also, in episode 10, there is Reisi and Mikoto on the ground with Suoh pinned under Munakata and their faces close enough to kiss.
Mikoto and Totsuka. Totsuka was Mikoto's most loyal follower before his death at the beginning of the series. Mikoto also wears Totsuka's earring as a remembrance.
Between Saruhiko and Misaki. Saruhiko left HOMRA because he was so tired and jealous of the rest of HOMRA, especially Mikoto for having Misaki's love, pride and attention, while he himself gets more and more ignored. It was so painful for him that it led him to a Love Makes You Crazy breaking point, where he would go to extreme lengths to hurt Misaki and even himself in front of Misaki, as he would rather have Misaki hate him than feel nothing for him at all.
Iron Woobie: Yata. Beaten 2 times by Kuroh, lost his target 2 times, best friend left him to join an opposing clan Scepter4, and Totsuka died in his arms. Despite all that, Yata keeps pushing himself forward and will even skip breaks that may be a bit detrimental to his health just so he can capture Totsuka's killer.
Jerkass Woobie: Fushimi. Often gives harsh criticism to others while belittling them. Doesn't show mercy even to his former allies. Won't even mingle with his own members from Scepter4. The only time he doesn't show the 'I've got a stick shoved up my ass' face is when he's with Yata (but then he's got the 'I'm bat shit insane' happy face). Bonus Points for being even meaner towards Yata and provoking a fight at every opportunity. Though underneath it all, Fushimi does hold some morals and cares deeply about Yata. He's really upset that he's no longer the only important person in Yata's life (the only person he has ever opened up to). Fushimi doesn't want to share Yata with anyone else. Leaving Homra in hopes that Yata will follow him into Scepter4. Upon failing to get Yata to follow him, he falls further into his jealously due to isolation and is willing use childish means to get Yata's attention.
Mikoto. He stops at nothing to avenge Totsuka's death, even endangering his own men and normal people's lives. On the other hand, he does try to keep his men out of it and showing Anna genuine affection. And then there is the fact that he is dying and his actions actually quicken his death.
Reishi turns out to be this. For most of the series he seems cold and calculating, and even a bit cruel. And then we realize the true extent of his worry about Mikoto, and see how desperate he is to save Mikoto from destroying himself. His expression when he realizes there's no way but to kill Mikoto is one of the most heartbreaking moments of the anime.
Sumika appears to have something for her friend Kukuri. She also blushed furiously when she saw Neko.
Sakura Asama has a very obvious crush on Chiho Hyuuga.
Like You Would Really Do It: Since it was obvious from the beginning that the story would revolve around Shiro, there's no way that Kuroh would be able to kill him so early on in the series.
Lost in Medias Res: One of the most common complaints against the first episode or the entire series so far. The narrative drops the viewers in a battle between some unknown organisations who also want to capture our seemingly clueless protagonist for no apparent reason. The situation between the clans and the reason Shiro is wanted among them are gradually explained.
Also, Kukuri and Neko have their cute moments as well.
Moral Event Horizon: Totsuka's killer really crosses it in episode 9, when he threatened to kill both Kusanagi and Yata, as well as to do things to Anna, who is an 11 year old child. Needless to say, Mikoto wasn't pleased, at all.
Also Fushimi/Yata, since Fushimi is a Stalker with a Crush who takes great delight in taunting Yata, to the point where he's essentially a walking Berserk Button for the kid.
Narm: In episode 11, when HOMRA psyche themselves up for the upcoming battle with SCEPTRE 4, they chant "No Blood! No Bone! No Ash!". Not only is the Engrish vaguely amusing, they're also stomping as they chant. The thing is, the stomping is synchronized, and due to the odd animation, it looks they're doing the can-can while they get ready to wage war.
Also in Episode 11, they shoehorn a panyshot into the scene where Shiroh gets stabbed. The drama was instantly diffused!
Homra chanting their battle cry, accompanied by a mournful male chorus in Episode 13. It's supposed to be heartrending, but it's trying a bit too hard.
Also when Shiro orders Kuroh to leave the island with Kukuri. It's supposed to be a tense, emotional moment, because it's likely Shiro is going to his death, but when Kuroh leaves he sort of...trots away, and it looks very silly.
Visual Effects of Awesome: The lack of information regarding the plot during the promotional stage along with the beautiful artwork and animation are what drew attention to the series at first.
The Woobie: Shiro. Turns out all his memories from ever since he was a child was one big lie. Just imagine calling your friend to realize that she doesn't even know who you are, calling home to find out that the number does not exist, and finally taking a train back home - to realize that where your home is meant to be, there is nothing but an abandoned stadium... This isn't even getting into how everyone wants him dead. And even when he's scared enough to cry, the poor guy refuses to give in and still strains to remain upbeat about it.
Yata and Anna by the end of the anime. They both seem to see HOMRA as a sort of surrogate family and have to deal with losing Totsuka before the series starts and Mikoto in the last episode. For Yata, there's also his issues with Fushimi.
Kuroh and Neko in the K:Black and White Side Novel. Both lost their parents when they were children. Neko used her powers to trick a couple into thinking that she is their child. She realizes that what she did was wrong when confronted by the Gold clan and undos the illusion only to have the couple brand her as a monster. She leaves deciding to live a solitary life as a cat from then on. After the death of Kuroh's parents everyone else who took him in seemed to have met untimely deaths or bad luck causing him to be left to die by himself. It's even sadder when Ichigen first met Kuroh and saw that the only way to save Kuroh from his misfortune was to turn him into his clansmen.