Jann is one of the main characters in the webtoon Dark Moon: The Blood Altar. He is a vampire and a twelfth-grade student at Decelis Academy, where he also serves as the enforcer of the school's Nightball Team. As a vampire, Jann possesses superhuman strength and the standard physiological traits of his kind.

In terms of personality, Jann is often described as being as solid as a rock. Compared to his brothers, he comes across as somewhat closed off, blunt, and direct. He is known for being an action taker rather than one to deliberate at length. However, beneath this tough exterior lies a deeply thoughtful and considerate individual. He cares for his brothers with his whole heart, and his loyalty to them is a core part of his being.

Jann's primary motivation is the safety and well-being of his brothers. This protective instinct drives many of his actions throughout the story. He is often cautious and wary of outsiders, believing that it is best for the group to keep their distance from other students to protect their secret. This stance puts him in opposition to more open-minded brothers like Heli, especially regarding the newcomer Sooha. His role in the narrative is as a key member of the group of seven vampire brothers. He acts as a steadfast supporter and a powerful enforcer, using his strength to protect his family when they are threatened by external forces like rival vampires or werewolves. As the story progresses, his initial resistance to forming bonds with humans softens as he becomes entangled in the events surrounding Sooha and the dark history that links them all.