Belle Tsukiyono is a character from the anime and manga series who serves as the Chief of the Anti-Demon Corps' 3rd Unit. She is a young woman with long blue hair, a fringe covering her forehead, and two small pigtails on each side of her head adorned with beads. Her eyes are orange in color, and her physical stats include a height of 156 centimeters with a birthday of March 30. Her typical attire consists of the Corps uniform, which includes a navy blue militia tunic, a short skirt, white gloves, and thigh-high boots. Following a severe attack by the character Fukuma, her body was covered in numerous cut scars, including a prominent cross-shaped scar on her right cheek and another across her left eye, though these were later healed and removed due to her self-healing abilities.

Bell is defined by her extremely timid and frightened nature. She is constantly anxious about failing to lead her unit properly and lives in fear of being mocked or scolded by the Corps Commander, Ren Yamashiro. Her speech pattern is distinctive, as she consistently refers to herself in the third person. This lack of confidence is deeply rooted in her background. Her childhood was difficult, as she was ignored by her parents and frequently bullied by classmates for being weak-willed. While growing up, she would often visit a shrine to wish for a strong supernatural ability, hoping it would allow her to stand out and compensate for her perceived cowardice. Her wish came true after consuming a Peach from the alternate dimension known as Mato. After her ability was discovered, she was scouted by the former commander, Tobera Azuma, to join the Anti-Demon Corps. Initially, she found praise and admiration from her peers. However, upon meeting the other unit chiefs, she realized her power seemed insignificant in comparison to theirs, causing her self-esteem to plummet back to the levels of her childhood.

Despite her low self-esteem, Bell wishes to remain with the Corps and befriend all its members. Her primary motivation shifts from a desire to simply stand out to a genuine desire to protect her comrades. This change in motivation begins to cultivate a sense of courage within her. Within the story, her role is that of a leader who struggles to assert herself. Due to her lack of confidence, she is considered the weakest chief in the Corps, unable to fully utilize the vast potential of her ability and suffering a humiliating defeat at the hands of Fukuma. She is often under the direct and intimidating influence of Commander Ren Yamashiro, who has been known to single her out for special training and "comfort," making her deeply afraid of the commander. Bell also develops a significant relationship with the main protagonist, Yuuki Wakura. During joint training sessions with his 7th Unit, she bonds with Yuuki, who helps her gain confidence. Yuuki comes to value her as a true comrade, and their relationship deepens through the series' reward system, which involves physical activities like stretching, as well as more intimate acts such as kissing and licking each other's bodies.

Bell's notable ability, granted by her Peach, is named Canopus. This power allows her to extract the life essence from any material object, instantly destroying it. Furthermore, this skill grants Bell a form of immortality, as she cannot die from any physical wound, no matter how severe, unless her ability is somehow nullified. Despite this incredible power, her timid nature prevents her from unlocking its full potential. Through her ability, she can also transform Yuuki into a slave form called Hidden Moon. In this form, Yuuki gains a smooth, regal appearance with crescent moon ornaments and chameleon-like features, granting them both the power of invisibility. Beyond combat, Bell enjoys looking for good restaurants and relieving stress by eating delicious food, with sushi being her favorite. She also spends her free time browsing the internet. Her surname, Tsukiyono, carries a meaning related to a moonlit night field.