The No Longer Human serial killer of Kyoto and member of the Zerozaki clan: Hitoshiki Zerozaki. Notoriously known as the Prowler during the Kyoto serial murder case. Hitoshiki is a man with a small stature that kills for the sake of killing. Soushiki Zerozaki and Hitoshiki have a somewhat brotherly relationship, though they've grown distant. In general, he doesn't have many friends as a serial killer, though Iori Mutou could be considered one, as well as Ii. Another killer, Izumu Niounomiya, is a friend and rival of Hitoshiki. 

Hitoshiki himself is eccentric, though he generally has a casual personality and way of speaking. He considers himself a brat and believes everyone else was once a brat. When he and Ii meet, he calls Ii a doppelganger as they are essentially identical, yet so different. Hitoshiki is later described as the mirror image of Ii, and what Ii would be like if he didn't hold back. As a Zerozaki, Hitoshiki has a desire to kill anyone he meets without remorse, though he is capable of holding himself back. Like Ii, Hitoshiki has a catchphrase where he often says, "What a riot," which contrasts against Ii's "Nonsense."

As both a Zerozaki and a serial killer, Hitoshiki has a couple abilities and tools at his disposal. In the vest he wears, there are many knives placed all throughout it, which complements his mastery at using knives. To go along with his knife expertise, Hitoshiki is also able to utilize string, making a nearly undetectable trap. Unfortunately, with all his prowess in killing, he cannot do much against Ii, as they can counter each other and will just end up in a stalemate. ~!Hitoshiki's knife finesse has made him able to hold his own against Jun Aikawa. Despite this, he cannot defeat her, thus he escapes. The two later come to an agreement where Hitoshiki vows to stop killing to continue living and tells Jun Ii's solution to his own problem during the time.!~ ~!When Hitoshiki was born, his parents both died. His parents were Hataori Zerozaki as his mother and Zeroshiki Zerozaki as the father. As they died after Hitoshiki's birth, Soushiki began to raise him.!~

Now that he’s a cool college student, our anti-hero Iichan thinks his crime-solving days are behind him. Cynical, sarcastic and minimally engaged in his studies, Iichan is much more interested in his own feelings of disaffection and isolation. But despite his resolve to remain aloof, he’s pulled into the narrative when he encounters and bonds with a serial killer named Hitoshi Zerozaki – a homicidal maniac with the soul of an artist whose talent is on display at the grisly scenes of his crimes.
 
(Source: Kodansha USA)

The No. 1 Killing Name, "Niounomiya", has finally arrived!
 
".....Specifically, what are you researching, Assistant Professor
Kigamine?" 
"——Researching not dying."
 
Invited to monitor the bizarre research on Kuchiha Madoka—a girl who lives eternal—Ii, the Nonsense User, visits the ruins of a clinic in northern Kyoto with antique apartment dwellers Ichihime Yukariki and Kasuga Kasugai.
 
However, what awaits them there is a terrible "fate" itself!
 
The Niounomiya siblings, the number one killers in the world, make their debut in this exciting new coming-of-age story.
 
(Source: Kodansha, translated)

It may be true that where there is a beginning, there is an end, but it is too shortsighted to think that because there is an end, there must have been a beginning. In fact, the opposite is true. Most events have already ended even before they began, and they are closed even if they are not opened. I, a sincere and honest person who dares not speak truth as truth, dares not speak fact as fact, and knows the virtue of silence better than anyone else, will ascend a certain staircase in September. The Thirteenth Staircase. It was Kino-Raichi, Noise, Emoto Sonoki, Mio-tsukushi Takami, and Mio-tsukushi Misora. However, what awaits me at the top of the stairs is so ridiculous and so nostalgic… in this sixth installment of the "Zaregoto" series!
 
(Source: Kodansha, translated)

Third ranking of the Killing Names of The Violence World, the Zerozaki Clan is infamous for their indomitable family unity. Each of its members exhibit combat prowess when it comes to saving one of their kin. Kishishiki Zerozaki is one member of the Zerozaki family, utilising a bat covered in nails to brutally murder his targets. He calls his weapon "Seamless Bias (Foolish Praise)". 
 
His next target was supposed to be just like any other target, though he was forced to bring Hitoshiki Zerozaki with him as a learning experience. It was supposed to be a standard mission, but now he faces a problem when he discovers that he has become prey to a formidable tactician and a ruthless berserker.

The forefront of new youth entertainment! "Now then, let's commence the Zerozaki"
 
The Zerozaki Clan is a family of demonic killers, ranked third among the Killing Names. The eldest brother whom is a leader of the clan is the user of Suicidal Tendencies (Mind Render)—also known as the Twentieth Hell—Soushiki. What awaits him on the other side of the breathless turmoil......?! The forefront of new youth entertainment is here!
 
(Source: Kodansha, translated)

Iori is a high school girl who doesn't know what she wants to do with her future, and tends to run away from things. One day, she is attacked by strange dead-eyed people on her way to school, only to be saved by an equally mysterious long-haired man. Later that day, her friend at school, Jion, seems to fall under the same murderous influence. To her surprise, she finds herself capable of defending herself from his violent attack. Afterward, the long-haired man she met in the morning, Zerozaki Soushiki, arrives once more, this time to invite her to become his little sister. What has Iori become involved with, and will she be able to survive this change to her life?


What if Monogatari's Ararararagi, Zaregoto's Ii and Jun "Humanity's Strongest" Aikawa, and Okitegami Kyouko no Bibouroku's titular forgetful detective all attended school together? In 2002, NisiOisiN won a Mephisto Prize prize for his debut novel Zaregoto, Book 1: The Kubikiri Cycle. Part of the 15th anniversary celebration will be 4-panel crossover gag manga Seishun Kijin-den! 240 Gakuen (240 is a pronunciation pun - 240 can be read as "Nishio," so "Youth Oddball Story! Nisio Academy"). 
 
(Source: Crunchyroll)

The Zerozaki Clan is a family of demonic killers, ranked third among the Killing Names.
 
A boy with eyes like that of a dead man and a serial killer with a tattoo on his face. The story of their encounter and the never-before-told truth of the Kyoto serial killer case is finally revealed! The motivation of Zerozaki Hitoshiki, and its miserable ending......?!
 
(Source: Kodansha, translated)

"It might not be bad to commence the Zerozaki."
 
The strongest "Sound User" appears.
 
The Zerozaki Clan is a family of demonic killers, ranked third among the Killing Names. Zerozaki Magashiki, known as "Girly Tastes (Bolt Keep)", senses a danger creeping up on the clan and finally appears on the stage. What will happen to the unity of the clan? The battle of the "sound user", Zerozaki Magashiki, begins now! The forefront of the new youth entertainment is here!
 
(Source: Kodansha, translated)

The Zerozaki Clan is a family of demonic killers, ranked third among the Killing Names.
 
Zerozaki Hitoshiki, 17 years old, during Spring when he was freest and in his prime. The six Cursing Names, the counterparts to the seven Killing Names—the Tokinomiya Hospital, the Tsumiguchi Firm, the Nukumori Garden, the Shibuki Factory, the Kino Division, and the Toganagi Faction. Hitoshiki inevitably gets caught up in a battle between a messy alliance and his brother, Zerozaki Soushiki.
 
(Source: Kodansha, translated)

The Zerozaki Clan is a family of demonic killers, ranked third among the Killing Names.
 
Zerozaki Hitoshiki, who attends junior high school with the name "Migiwame Toshiki", meets someone who claims to be his friend. The upcoming ace of the Niounomiya Performance Art Troupe, Niounomiya Izumu, ranked number one among the Killing Names. What "request" will come out of that mouth of his......?!
 
(Source: Kodansha, translated)

The Zerozaki Clan is a family of demonic killers, ranked third among the Killing Names.
 
Having just become siblings, Zerozaki Hitoshiki and Mutou Iori attack Aikawa Jun—Humanity's Strongest Contractor—with the best intentions. But, as a result, get caught up in her work! They're headed towards the domain of the second-ranked Killing Names, the Yamaguchi Folks, on the island of Taiyakujima. Therein lies the Lifelong Undefeated Crystal Kaiser, Rikka Kajumaru.
 
(Source: Kodansha, translated)