The Leader of the Heavenly Demon Cult and Guest's grandfather. He possesses immense martial arts prowess and is naturally the strongest within the Cult (though it is said he is weaker than the Supreme Demonic Empress, who has left the Cult). His skills are said to be on par with the Head of the Gale Clan, and he utilizes the Nine Fire Demonic Arts (through the final stages). He awakens and actively utilizes the Spirit of the Heavenly Demon. Although the Great War ended 20 years ago, he still harbors the dream of conquering the world.

The Young Cult Leader of the Heavenly Demon Cult. He is Yu Jin-cheon's eldest son and Guest's father, as well as Yu Seol-ha's older brother. He worries that his father's dream of world conquest will lead to massive loss of life. Among the demonic practitioners, he is quite righteous. He has mastered the Nine Fire Demonic Arts. His primary weapon is the Heavenly Star Sword, which is a staggering 3 meters long. He cherishes Guest deeply.

Yu Jin-cheon's daughter and Guest's aunt. She left the Cult for love and lived in hiding as a fruit merchant with Jeok Su-rin, giving birth to their son, I-geon. I-geon describes her as the most beautiful person he has ever seen. She has mastered the Nine Fire Demonic Arts. She uses the Hell Blade as her weapon.

Yu Seol-chan's wife and Guest's mother. She is usually quiet, but once she gets angry, even Yu Seol-chan cannot stop her. She has a very good relationship with her husband. She cherishes Guest deeply.

20 years old. The son of Jeok Su-rin and Yu Seol-ha, and Guest's cousin. Dreaming of world conquest, he recently founded a sect called the Blue Heaven Gate in Wuhan. His personality is said to be most similar to his maternal uncle, Yu Seol-chan. He has a habit of lightening the mood only to ruin it immediately. He possesses martial arts strength beyond his years. He can use the Galaxy Meteor Sword Style learned from his father and the first half of the Nine Fire Demonic Arts learned from his mother. He has not yet awakened the Spirit of the Heavenly Demon. His parents call him 'Geon-i,' and he is currently in a flirtatious relationship with Jeong Cha-ryeon of the Righteous Sword Gate.

Yu Seol-ha's husband and Jeok I-geon's father. He is Guest's uncle-in-law and the Young Lord of the Gale Clan. He uses the Galaxy Meteor Sword Style. His weapon was the Gentleman's Sword, which he later passed down to Jeok I-geon. He is usually quiet. He is the type to get angry silently, which makes him quite intimidating. Coming from the Orthodox factions, he places great importance on following rules and etiquette.