Kaname is a tall and attractive boy with pale skin, stylized blue hair, and glasses. When he is using Nijimi Anazawa's stick, the tips of his hair becomes white and the stick's emblem, an ace, is displayed across his eyes and wrist.
On the outside, Kaname presents himself as a polite, studious, kind and caring boy in front of his parents and teachers.
However, in private, he is a sadistic and sociopathic boy; he loves to see his adoptive sister in pain and regularly beats her as an outlet for stress relief. He abuses her because he knows there will not be social consequences for that behavior and this shows in other interactions as well. He likes being in control and delights in his ability to hurt people and make them hurt themselves. Despite his cruelty to Aya and hatred towards his father who Kaname greatly desires to kill, Kaname genuinely loves his mother as he does not want her to be killed.
He is a misanthropic boy. His internal monologue regularly shows that he finds other humans to be a waste of time and potential. He thinks about their activities and concerns as foolish. He finds being expected to deal with them to be irritating and difficult. He doesn't relate to other human beings well and considers himself above them, going so far as to wonder if he's a god instead, merely trapped in human form. The series presents this as related to his father's constant physical and mental abuse; Kaname thinks that it is so wrong to abuse someone like him that he wants to see his father in pain, despite the external performance of being a 'father's boy'.
He is also an intelligent, resourceful and organized boy, most of his actions being well thought out in advance. Hei will do whatever will be most advantageous for him at the time, regardless of how wrong it may be or how distasteful he may find it.
Despite all of his abuse and bad doings, he does seem to care about saving his mother and adoptive sister before the site admin is able to get them. After being freed from his father's control, Kaname's hatred of him reached its peak as he violently punched him despite him being unconscious and vowed to make him suffer before killing him.
After his father died, Kaname expressed relief over no longer having to deal with him and even engages in a proper conversation with Aya for the first time. However, he still expresses bitterness and is shown to be ungrateful to Aya for saving his life, and instead mocks her for not knowing that they weren't related all this time, and that she no longer has anything to fight for. He displays no remorse for any of his actions, selfishly requesting Aya to protect him from Tempest and even sarcastically apologizing about killing Nijimi.
When Aya steals the majority of his remaining lifespan to prevent him from using a stick, he initially lashes out in anger. It isn't until Aya reveals how much she went through to protect him from ultimately suffering a mental collapse and will to protect both him and his mother that Kaname quietly accepts the circumstances without struggle.
Later it was revealed in the Chapter 138, the true extent of Kaname's guilt and remorse for all the pain he inflicted to Aya. Just as Aya was making her Time Jump to the past to save all her friends from misery, Kaname used the last of his remaining Lifespan to use the Panties to give Aya one last "Order", this order was embedded so deeply into Aya's mind she had no chance of ever going against or break free from it: He ordered her to never be able to save the world and her friends, unless she also obtained her own happiness in the new world thus ensuring that she herself will never be cursed with misfortune in the new timelines she created.
In the new timeline, because he no longer has to endure the stress of his father's abuse and expectations, Kaname has become a more kind hearted boy, as he has shown to smile genuinely at his father after being told to relax and have fun. While he has shown to be impatient, it is highly possible that he has a much better relationship with his adoptive sister than before.
Kaname was born from Jirou Asagiri and Momoko Asagiri, six years after their marriage, when he was 2 years old, his mother adopted a newborn girl named Aya, after his biological sister died before the birth due to a miscarriage caused by his father.
Kaname is introduced for the first time as Aya's primary abuser at home; he refers to his adoptive sister as his "Punching bag" or "Sand bag" and says that her only purpose in life is to be his stress relief. He regularly ties her up and punches her.
His father raised him with the idea of academic perfection being necessary, in order to ensure that he gets accepted into Tokyo University. He's regularly abused by his father for failing to meet his expectations, including being hit for getting 98 out of 100 on a practice exam.
He spends a lot of time studying and is very stressed by the effort and expectations. His relationship with his father is strained by the abuse and expectations; Kaname is deferential to him to his face, but privately judgmental of his failure to get into Tokyo University and of his abusive behavior. His relationship with his mother is better, as he perceives her as loving him.
From the Collection of Sticks, Kaname was given a Teddy Bear Stick by Kichiro that has the power to fire powerful energy blasts from its eyes.He attempted to use this Stick against the King to no effect.
- Kaname is the first non-magical girl to use a Stick.
- So far, he has killed Keisuke Naoto and Nijimi Anazawa in both anime and manga.
- Kaname's hobbies include study, sports, Go, Shogi and walk.
- Kaname likes curry rise, bath and his mother.
- Kaname dislikes animals and his father.
- His name Kaname means pivot, cornerstone, accessory and keystone.
- His surname Asagiri means morning fog.
- It is unknown why Kaname hates animals, it is implied that he find them ugly and stupids.
- His hatred toward animals is the reason that led Aya not to adopt Mya.
- He and Himeji Wataru, a character from Mahou Shoujo of The End have one thing in common.
- Their obsession of the idea of becoming/being God. (Though, it was later revealed that Himeji actually wanted to become human).
- It is unknown why he lives up to his father's expectations. It might have to do something about disowning, or even killing him.
- In the Chapter 90, he seemed to care when he was told that his parents were in danger, he called his mother to see if she and the Panties were okay, considering his mother was always caring and not abusive.
- It was eventually revealed in the Chapter 93 that Kaname does love his mother, in his thoughts, he mention how he couldn't care less if the site administrator skill his father but he refused to let his mother get killed.
- In the Chapter 135, it was shown that due to the fact that Nijimi not suffering any misfortune she never became a magical girl, consequently, Kaname never killed her and never stole her Stick, without the Stick he never killed Keisuke Naoto, and his father did not steal the Stick and never died for use excessive.
- In the Chapter 138, Kaname lost his lifespan by casting magic so that Aya won't be unhappy with Panties's ability, which had been regaining the moment just before the Earth collapsed and Aya tried to go back in time with a stick.
- In the final chapter, Kaname has shown to become a more thoughtful and genuinely kind boy as he no longer has to put up with his father's high expectations and abuse. It's possible that he has a much better relationship with his adoptive sister as he goes to the beach with Aya and her friends. He is shown being relentlessly chased by Kiichiro Misumi in the distance.
- Kaname's birthday is on January 13.