Yukine (雪音, Yukine?) (lit. sound of snow), whose real name is Haruki Tajima (田嶋春樹 Tajima Haruki), is one of the three main protagonists and one of Yato's Shinki. When the name Sekki is called, he transforms into a silver Ōdachi, the handle of which is loosely wrapped in bandages. After becoming a Hafuri Vessel (Blessed Regalia), his new Shinki form is that of two twin katanas, shorter than the original, but with the same design.
In his human form, Yukine appears as a young teenager with short, messy hair. His hair is colored gold both in the anime and manga colorations. However, his eyes are reddish-orange in the anime and a yellow-amber in the manga.
He is shorter than both Yato and Hiyori. His height is 147.4cm (or 4'10") according to the Animation Visual Book released for the anime. Despite being physically 14, it seems that Yukine appears even younger than his age. This can be noted from his small stature, Hiyori's shock when she realized he was only a year below her in school, and his previous neighbor's remark that he was small for his age in middle school. This is likely due to malnutrition and stress resultant from his father's abusive treatment.
Upon his first summoning, Yukine wears a simple white robe, resembling a Japanese shinishozoku. He is later depicted with a blue hoodie, loose grey jeans, and teal patterned knit cap.
Later on, he changes his attire to a white T-shirt, dark blue jeans, and a green knee-length jacket with a fur-trimmed hood. While as the manga progresses, his outfits are not always consistent and vary to all sorts given to whatever he is depicted with.
Yukine's hair becomes black and he grows black claws while in his new form as Hagusa. 
Yukine is first portrayed as being a bit cold and cruel. He is clearly upset and annoyed at the fact that he died and became Yato's weapon, complaining about staying with someone like him. As a result of this and the fact that people cannot see him well, Yukine takes advantage of this and other people, stealing money, clothes, and even betraying Hiyori. The reason for this is Yukine's jealousy of the living, as he is upset about the fact that he is dead, and cannot make friends and learn what other students do, leading him to feel rather entitled and ungrateful.
When Yato is forced to punish Yukine through Ablution, Yukine confesses all of his sins and apologizes sincerely, and escapes the temptation that hurts Yato as his Shinki. Yukine is visibly more upbeat after his punishment, becoming more outgoing and befriending Hiyori more and requesting to learn what she does in school. Yukine also is more diligent in his work as Yato's Shinki, working part-time for Daikoku to earn money for the two of them.
Despite this, Yukine is still a bit sarcastic and can be prone to outbursts when he is upset, especially after one of his few friends, Suzuha, dies. When Yato was missing, Yukine withdrew, refusing to worry about Yato and attempting to suppress his feelings so he wouldn't sting Yato once again. He instead busied himself learning how to be a better Shinki from Kazuma and tutoring from Hiyori. This shows that although Yukine still holds true to his sarcastic and edgy personality, he remains incredibly compassionate for those he forms bonds with, and that he is quite diligent.
It has been shown many times how insecure Yukine truly is. It is highly evident that he seeks validation from the authority figures in his life, especially Yato, and he has a deep-rooted fear of abandonment, likely stemming from his abusive family situation when he was alive. This leads to him being incredibly upset when Yato uses other shinki, especially Nora, as he views it as a betrayal and abandonment.
As his Lead Shinki, Yukine has shown to be very strict with Yato especially after Yato's declared his resolve to change his ways. Yukine's methods of dealing with Yato may appear harsh, but in reality Yukine is strict in order to help Yato improve himself and keep him on the proper path, since he cares for him and wants to see him reach his goals. Yukine also shows great concern and protectiveness for Yato. When he discovered that the sorcerer, Yato's father, was also his lifeline, he kept Yato from killing him. Likewise, he warned Yato against meeting Kazuma again after he got information from Yukine by force. He also urged him to fight Bishamonten and stop her when she was fighting with Fujisaki.
Yukine's jealous tendencies and fear of abandonment never fully disappear, and as such he was both upset and in denial when he found Yato was employing Kazuma as his shinki behind Yukine's back, though he denied this when confronted by Nora.
Because Yukine is insecure, curious, and approval-seeking, he is also to manipulate. When Fujisaki claimed that he would care for Yukine without abandoning him and would help him learn whatever information he sought, Yukine willingly became his shinki, despite previous confrontations with Fujisaki.
After becoming Fujisaki's shinki and taking up the Hagusa name, he is shaken after learning he did not have the loving family he wished for. Instead, he learns of his abandonment, his father's abuse towards him, and his eventual murder, and decides to seek out his father in order to learn why he killed him. He displays a lack of interest in Yato at this point, and easily attacks him since he believed Yato had abandoned him in the same way his own father did.
Skills and Abilities
Yukine is a very powerful Shinki. He was able to create a Boundary on his first try which Yato commented was unheard of. Even Kazuma had to practice for a long time before he was able to create a decent Boundary. He's strong enough to warrant Ebisu and Yato's father's attention and praise to the point where they've both announced their desire to claim Yukine as their own Shinki. Yato becomes worried about the latter's intentions and suggests that he and Yukine move to his small plot of land in Takamagahara.
- Rend (Zan): is a skill he obtains as Yato's sacred weapon Sekki. When Yato uses Rend, he is able to slay and exterminate phantoms.
- Severance (Zetsu): is a skill he obtains as Yato's sacred weapon Sekki. When Yato uses Severance, he is able to cut off the bonds between a human and things/other people. He uses this skill to sever the bonds between Yusuke Urasawa and Kofuku.
- Boundary (Kyoukai 境界): is an ability Shinki are available to use. Using his fingers, Yukine can draw a line and create a "boundary line" that prevents any gloom from coming past it, which is one of his only defensive mechanisms.
- Restraint (Baku 縛): Yukine has the ability to cast a binding restraint on a target. This ability appears to take the form of invisible chains. According to Daikoku, only Hafuri Vessels (such as Yukine and Kazuma) can use this ability. This ability greatly affects the other Shinkis that are not Hafuri Vessels because of superiority. Nevertheless, when a Hafuri Vessel loses his confidence and has much insecurity; like when Yukine was almost defeated by Kugaha, they can also be defeated in a boundary battle.
- Spell/Chant/Song: A skill that he obtained from his training with Kazuma. It enables him to cast spells that can be used as a protection or to attack; for example, a song Yukine used in dousing the flames in the manga. It can also summon spirits like Nora used in the manga.
- Yukine's names, Yuki (雪?) means "snow" while Yukine (雪音?) means "the sound of the snow".
- Yukine has a phobia of night and dark rooms, probably due to having his final moments being suffocated in a refrigerator in his human life.
- It is possible that the reason as Sekki, the bandages on the hilt are associated with his past life. There is a single frame in Yukine's memories where an arm is seen with bandages all over the place.
- Yukine and Kazuma are the only known Hafuri Vessels. In this case, Yukine changed from being an Ōdachi to a katana and wakizashi.
- His character song is Catch Ball which was sung by his voice actor, Yuki Kaji.
- Hiyori guesses in Chapter 13 and Episode 1 of Noragami Aragoto, judging by his education level, that he died in his second year of middle school.
- He is very sensitive about his short height.
- Daikoku pays him 500 yen an hour for helping out part time at Kofuku's.