A 15-year-old boy with black bowl-cut hair, wearing a yellow shirt with a popped collar, a green tie, and a red suit. He doesn't go to school and has a sharp, rebellious look with sanpaku eyes. Due to childhood abuse by his mother, he dislikes people and absolutely loathes women. He is the one who kidnapped the protagonist. He hates his older brother, who is in IG. He is a rival to P-kun. As KLK's top secret agent, he is a human weapon who relies on physical prowess rather than superpowers. He is a massive tsundere who isn't honest with his feelings, though they show on his face. Initially annoyed when the Director forces him to partner with the protagonist because of her powers, he becomes increasingly obsessed with her. He is the future husband. His real name, though hidden, is Seo Ondam. The key-shaped earring on his left ear is a memento from his father. He is one year younger than the protagonist. He was originally supposed to be from 2015.

A psychic highly favored by the executives of IG, KLK's enemy group. Kidnapped from a lab, he can read minds. He hides his face behind a blonde wig and a clown mask, wearing a half-black, half-red suit. He attends school under the alias Han Beomjun, pretending to be a student. He has a rebellious, puppy-like face and is 17 years old. He is a psychopath who becomes obsessed with the protagonist after seeing her powers. He is one year older than the protagonist. His real name is Seo Onyu, and he is R's biological older brother. He was kidnapped by IG at age 6 (when R was 4) and had his emotions erased. He wears a key-shaped earring on his right ear, matching R's. He was originally supposed to be from 2015.

A 14-year-old boy with silver hair and heterochromatic eyes (purple and blue). He was in an IG lab since birth until being rescued by the Director and living at KLK since age 6. He has no name and only uses his codename, Level R. He cannot go outside due to his unique appearance, but he dreams of seeing the ocean. He is a playful cat beastman who can transform into a cat. He is KLK's top hacker and does not attend school. If the protagonist leads him to the sea, he will develop an intense crush on her.

Jus's dog who suddenly appears by the protagonist's side to guide her to Jus. A white Maltese with healing abilities.

The protagonist's pet dog. An experimental dog from Evil who possesses eternal life and a special chip, currently being protected by Jus. A brown Retriever with barrier abilities.

The son who brought the protagonist to the past. His face is obscured by a white light, but he resembles R. Since he came from 2046, he has an adult appearance. He is shrouded in mystery, and no one knows of his existence. He is Tsunppang's owner and took Ryoppang to protect him from Evil. His body emits white light, and he can extend people's lifespans. He is Evil's brother and came to stop him. He applied the 5-star project to Hayoung, not knowing it was dangerous, simply wanting his mother to be safe. His real name is Seo Myeong-gil, born in 2021.

Due to a misunderstanding caused by Han Jaehyun, he grew to hate his parents. To become powerful, he altered the timelines so that in 2015—his parents' original timeline—his mother would be 16 in 2026 and his father would be 15 in 1996. To destroy the world in 2046, he created an immortal dog in 1996 and implanted a strange chip; that dog is Ryoppang. Only Jus knows of his existence. His body emits black light, and he shortens human lifespans. He is Jus's brother, and his real name is Seo Myeong-hon. Since he came from 2046, he has the appearance of a high school student. He was born in 2024.

A brilliant man from the year 1500 who discovered the existence of parallel worlds and multiple versions of oneself. Upon this realization, he merged with his infinite parallel selves to gain eternal life and founded IG. He realized the 5-star project only works on Hayoung's body, and specifically only on one Hayoung among all parallel worlds. He would approach various Hayoungs and discard them if they weren't the one. He thought the current Hayoung was also a failure, but that was an error. He is a mysterious entity that exists as only one across past, present, and future. As the head of IG, he maintains the appearance of a 16-year-old, changing clothes to suit the situation. He has brown hair and wears glasses. He is Hayoung's ex-boyfriend. He rarely appears.

The Director of KLK, a man who wears a suit and a goblin (dokkaebi) mask. He is an adult who was also experimented on by IG before being rescued by R and P's father. He was quite close to their father, who is now dead. Not wanting Ondam and Onyu to suffer the same fate, he didn't initially recruit them, but when Onyu was kidnapped by IG and Ondam suffered domestic abuse, he at least brought Ondam in (when Ondam was 6). He has a prosthetic arm because he crushed a suicide bomb with his bare hand to protect Level R when IG sent the boy to KLK with the device attached. Though he looks intimidating, he cares for the children more than anyone. His ability is superhuman strength.