Guren Ichinose

Kujakumaru: This sword is called Kujakumaru, and Guren Ichinose wielded it at the age of fifteen. It was a Book of Catastrophe 1: Guren wielding Kujakumaru
Kujakumaru was a relic passed down through generations of the Ichinose Clan. It was a sword sealed with the curses of those who had been beheaded by it. The sword could prevent the enemy from absorbing the impact of an explosion created by a talisman placed on the blade, which supposedly resisted any curse of the Hīragi Family. Once the seal was lifted, the enemy would soon be cursed by this weapon, and their body would turn red. As a result, the curse would eventually destroy the enemy's body, tearing and atomizing their flesh.

Paralyzing Spell: A disabling spell within a spell tag was able to paralyze both Yu and Mika after they were physically placed on their backs.

Illusion Spell: While fighting the demonic Yu and Mika, Guren, himself a demon, used a spell that allowed him to create an illusion of himself. This illusion could withstand considerable damage and served as a stratagem to get close to them. The spell was so convincing that Mika, who could see through Goshi's illusions, didn't notice it, and Yu's levitating weapons, which could lock onto a target, also sought out the double. The Ichinose family, and Guren in particular, possessed special enchantments, such as a talisman placed in the scabbard of his katana. By activating the enchantments through the sword's talisman, the sword would begin to glow with an intense crimson red.

Fudo Myo-o Spell: Guren has been adept at using enchantments on spell tags and talismans since his late teens. At sixteen, he can implant a talisman into his sword to increase the weapon's power and cursed ability. By synchronizing the talisman with the blade itself, he creates an unnatural explosion within the enemy's body, inflicting greater physical damage. Guren can also successfully implant one of these spell tags into a target's head when caught off guard or if the opportunity arises. In such cases, this type of spell is ancient, causing an explosion that occurs after a few seconds or seemingly at will before detonating.

He also specializes in other combat skills, such as the use of magic and magical seals, standing out for his proficiency in this field even among the Ichinose family. Furthermore, he is adept at their strategic use during combat. Guren possesses extensive knowledge of magic, as demonstrated by his ability to discern one of Goshi's illusionary techniques and anticipate Mito's Vajrayaksa Curse before easily countering it.

An expert in martial arts, Guren typically employs highly effective melee attacks while fighting with his sword, easily defeating his enemies. He defeated Shinya relatively quickly in hand-to-hand combat and was even able to overpower Mika like a true vampire, wielding his sword while, physically enhanced by Mahiru-no-Yo, he fought for a time using only his bare hands.

Guren, an expert in experimentation since his teens, has proven to be an intelligent scientist, capable of developing Cursed Equipment in his adulthood. Thanks to this, he has even managed to create a method with an extremely high success rate for developing humans capable of wielding Black Demon Series weaponry. Guren is also an exceptional strategist and leader, generally leading any team he joins, partly because he has cultivated a circle of friends who serve him out of loyalty, regardless of rank, as he helps them. He is known for having backup plans, such as administering the drug to Yu to activate her Seraph genes should they find themselves cornered. Highly analytical, Guren is able to quickly deduce how to counter a difficult situation, such as ordering the group to retreat from overpowered enemies. Even Kureto, when still a teenager, recognized Guren's great intellectual and political acumen. After knowing each other for about eight years, Guren became his right-hand man in carrying out his missions. Guren also masters the five-man combat formation called the Moon Demon Company, which he primarily uses as a defensive tactic within his squad. He is highly skilled at deceiving others, as evidenced by the fact that no one, not even Shinya, but only Kureto and Ferid, knew of his demonic nature until he openly revealed it.

His kindness is the reason Guren hasn't been completely honest with his squad when they're together. Even more reserved, Guren concealed his second personality to such an extent that not even one of his closest friends, Shinya, noticed it. Remaining kind was another reason why his original personality hadn't yet been completely overtaken by his demonic second personality, and it continues to exist. However, he has since kept his emotions under control on a daily basis, taking care to project a positive image so as not to worry them.

When it comes to being manipulated by his demon, it is by Mahiru

During his childhood, Guren's view of life was simple until Mahiru Hīragi entered his life. Aware of the barriers that separated them due to their family origins, when he was forcibly separated from Mahiru and treated with contempt for belonging to a lesser branch of the family, Guren felt guilty for being essentially too weak and lacking the strength to have tried to reach what he desired then: Mahiru.

Guren is a tall young man with medium-length black hair, styled in a wavy, messy mullet, with slightly disheveled bangs parted in the middle, and striking violet eyes. Some girls, who are in love with him, consider him quite handsome. He is usually seen in his school uniform.
Sometimes he wears his hair combed back during battlefield skirmishes, but more often he is seen with it slightly disheveled, his bangs falling over his forehead. Guren wears the standard uniform of the Imperial Japanese Demon Army, tailored to his stature, which consists of a double-breasted, long-sleeved black coat with two rows of gold buttons down the front, with red details including epaulettes on the shoulders, buttonholes at the bottom, and stripes on the sleeves. Other decorative elements include gold pins and white fourragers on the right shoulder, attached to a stylized cherry blossom pendant at the center of the neck, and two bars with the unit insignia medal below them on the left. Guren wears white gloves, a black-on-white armband on his left arm, a red and white striped belt with a sword loop on the left side, and a gold belt buckle at the waist. In addition, he also wears the uniform trousers with two white belts around his left leg and black shoes.