Tsukune Aono is portrayed as a handsome teenage boy with a lean and athletic build. In the manga, he has black hair, brown eyes, and fair skin, while in the anime, his hair appears dark brown and his complexion is slightly more tan. His standard attire is the Yōkai Academy male uniform, consisting of a white button-up shirt, a red necktie, a green blazer, tan trousers, and dark brown loafers. In certain anime episodes, he is also seen wearing uwabaki slippers with green soles. Outside of school, Tsukune typically dresses in a green button-up shirt over a white T-shirt, paired with brown cargo pants and white sneakers. During beach outings, he wears dark blue swim trunks and sandals.

As Tsukune’s body adapts to supernatural influences, his appearance undergoes several significant changes. After receiving Moka Akashiya’s blood, his eyes temporarily develop slit pupils, similar to those of vampires using their powers. Upon becoming a modified human, glowing blue lines resembling circuit board patterns appear on his skin during spellcasting, and his eyes may turn blue when activating yōjutsu techniques. Throughout the series, Tsukune acquires numerous scars from his battles, including a prominent X-shaped mark on his torso from an encounter with a monstrel possessing bladed arms.

His first transformation into a ghoul manifests with vampiric eyes and a black, web-like mark extending across his neck and face from Moka’s bite. When he experiences a complete, though temporary, transformation during his human modification ritual, he develops silver hair, white empty eyes, sharp fangs, and bat-like wings. His skin becomes predominantly black with red musculature and crack-like patterns on his face, arms, and torso. This monstrous form is later referred to by Kurumu as the “Jet Black Monster.”

As Tsukune continues to unseal his Holy Lock while aboard the Hanging Garden, his transformation into a ghoul becomes more gradual and chaotic. A dark layer of skin spreads across his body, wings begin to form, and parts of his body particularly his right arm—undergo erratic mutation. This instability is caused by the Shinso blood of Alucard flowing within him, transferred through Moka and her mother, Akasha Bloodriver. After completely removing his Holy Lock and gaining control over his powers, Tsukune achieves his final transformation as a Shinso vampire. In this form, he can alter his appearance at will, including turning his hair silver, giving his eyes slit pupils, and enveloping his body in a sleek black aura-like skin, while sprouting large, bat-like wings from his back. He also gains access to the Creation ability, allowing him to form a flexible steel-like armor over his torso and limbs for additional protection.

By the end of the manga, following the final battle with Alucard, Tsukune stops wearing his school jacket altogether, a visual reflection of his transformation from an ordinary human into a powerful Shinso vampire.

Tsukune Aono is depicted as a kind-hearted, gentle, and selfless individual with a strong sense of compassion. He is often described as sweet, caring, and somewhat naïve particularly in the early stages of the series. Initially timid and prone to getting flustered when interacting with girls, Tsukune gradually matures into a brave and determined young man, especially when it comes to protecting those he cares about. Despite being thrust into a dangerous world filled with monsters, he never wavers in his belief that coexistence between humans and yōkai is possible. His idealism and empathy drive his desire for peaceful resolution, and he often seeks diplomacy over violence, even in the face of hostility.

Though faced with numerous life-threatening situations, Tsukune is willing to put himself in harm’s way to safeguard his friends, and eventually sacrifices his own humanity to gain the power needed to protect them. His unwavering loyalty and willingness to shoulder great burdens earn him the deep respect and affection of many at Yōkai Academy, including Moka Akashiya, Kurumu Kurono, Mizore Shirayuki, Ruby Tōjō, and Yukari Sendo. Despite their romantic advances, Tsukune remains modest and passive in the face of their affection, often becoming embarrassed but never harsh in his rejections. He subtly turns down their advances out of consideration for their feelings, reflecting his chivalrous and empathetic nature.

Tsukune’s growing power as a vampire does not corrupt his core identity. Even after transforming into a Shinso vampire, he retains his belief that who he is internally matters more than what he is externally. His humanity persists in his actions and values, particularly his devotion to Moka. While he shows mercy and understanding to many of his foes, there are moments when his darker instincts emerge, especially under the influence of his ghoul form. He has shown lethal intent when necessary, such as during confrontations with the Black Parade ghouls or when using his Creation ability to nearly destroy Alucard, but these actions are often framed as acts of necessity or mercy rather than vengeance.

Ultimately, Tsukune remains a symbol of human compassion and resolve within a supernatural world. His development from an ordinary, nervous student into a courageous, powerful protector illustrates his emotional growth while maintaining the integrity of his kind and empathetic spirit.

Holy Lock (formerly)

Following his initial transformation into a ghoul, Tsukune was given the Holy Lock by Yōkai Academy’s headmaster, Tenmei Mikogami. This magical wrist-bound device was designed to suppress the unstable vampire blood within him, allowing him to maintain his human form while gradually adapting to his new powers. The Holy Lock served a dual purpose: it not only sealed Tsukune’s vampiric aura but also allowed him to safely access limited portions of that power when needed. However, overexertion could cause the Lock to suffer damage often indicated by a broken link in its chain.

As Tsukune grew stronger, he undertook specialized training under Inner Moka and Ruby Tōjō, eventually gaining refined control over his aura. This allowed him to activate his abilities without damaging the Lock. Upon becoming a modified human, Tsukune learned to manually release the Holy Lock’s seals through magic, granting him greater access to his vampiric powers.

In a pivotal moment, Tsukune tore off the Holy Lock entirely to save a mortally wounded Moka through a blood transfusion, embracing his transformation into a true Shinso vampire. It is later revealed by Alucard that the Holy Lock’s true purpose was not only to suppress vampiric energy, but also to safely facilitate a human’s transformation into a supernatural being by gradually adapting the body and suppressing harmful side effects.

First Seal Release: Under the tutelage of Touhou Fuhai, Tsukune learns to release the first seal of the Holy Lock. This enables him to access a greater degree of his vampiric strength, though it initiates a slow transformation into a ghoul.

Second Seal Release: After mastering the first seal, Tsukune progresses to the second seal. This grants him even more power, but also causes visible and dangerous mutations in his body, accelerating his descent into ghoulhood.

Belmont (formerly)
During the early stages of his training, Tsukune was temporarily entrusted with a legendary whip named Belmont, once wielded by a famed monster hunter. The whip possesses a unique magic-cancellation ability, allowing it to neutralize magical seals such as Moka’s Rosario and Tsukune’s own Holy Lock. By connecting his Holy Lock to someone else such as Ruby and channeling excess energy through the whip, Tsukune was able to access his powers without losing control. However, after completing training in Yōki detection under Moka’s guidance, Tsukune no longer relied on Belmont and ceased its use.

The given name Tsukune (月音) is composed of the kanji 月 (tsuki), meaning “moon,” and 音 (ne), meaning “sound,” which together can be interpreted as “sound of the moon.” Interestingly, “Tsukune” (つくね) is also the Japanese name for a popular dish teriyaki chicken meatballs, commonly found in bentō boxes, adding a humorous layer to his otherwise serious character.

His surname, Aono (青野), combines 青 (ao), meaning “blue,” and 野 (no), meaning “field” or “wilderness,” which can be translated as “blue field” or “verdant plain.”

Kyōko Aono

Kyōko is Tsukune’s older cousin, though their relationship resembles that of close siblings. During their childhood, Kyōko often involved Tsukune in risky situations, yet the two maintained a strong bond. She affectionately calls him “Tsuki,” while Tsukune refers to her as “Kyō-chan.” Concerned for his safety, Kyōko visits Yōkai Academy during the school festival to assess whether the school is truly dangerous. Initially under the impression that it was a school for perverts, her perspective changes dramatically after she encounters the truth behind the academy’s supernatural nature especially following her experience with Lilith’s Mirror. After Tsukune rescues her from the chaos that ensues, Kyōko realizes that he has matured and no longer needs her protection. Trusting in Tsukune’s judgment, she promises to keep the academy’s true identity a secret from his parents.

Moka Akashiya (Outer)
Outer Moka is the first person Tsukune meets at Yōkai Academy, and she quickly becomes the focal point of his affections. Although their initial connection is based on Moka’s craving for Tsukune’s blood remarked upon for its “uniquely tasty” flavor, their bond evolves into a deep and mutual affection. Despite his discomfort at her frequent “kiss bites” (stylized in the anime with the sound effect capu-chu), Tsukune allows her to drink his blood willingly when he sees her health declining. Over time, their emotional connection strengthens. Though often interrupted by the other girls or their own shyness, both Tsukune and Moka repeatedly come close to confessing their love. When Tsukune faces expulsion, Moka even declares she would rather leave with him than be separated, highlighting the depth of their bond.

Moka Akashiya (Inner)
Tsukune initially finds Inner Moka both intimidating and beautiful. At first, she is dismissive of him, viewing him mainly as a tool to remove the Rosario and assist in fending off attackers. Like her outer counterpart, she shares a preference for his blood. However, as the series progresses, Inner Moka’s frosty demeanor softens, and she begins to show concern and affection for Tsukune. Though too proud to admit it openly, she gradually falls in love with him. Her feelings become clear during a pivotal moment when Tsukune is on the verge of death, Inner Moka saves him by injecting him with her vampire blood, fully aware that doing so could cost him his humanity and turn him into a ghoul.

Kurumu Kurono
Tsukune first encounters Kurumu after hearing rumors about a seductive girl enchanting the male students. Kurumu, a succubus, initially targets Tsukune out of jealousy, hoping to win back attention stolen by her rival, Moka. Though she uses her Allure ability on him, Tsukune remains emotionally attached to Moka. Enraged, Kurumu attempts to attack him, only to be stopped by Inner Moka. When Inner Moka nearly retaliates with lethal force, Tsukune intervenes, telling her that he doesn’t believe Kurumu is a bad person. Touched by his sincerity and kindness, Kurumu develops genuine romantic feelings for him, marking the beginning of a long-standing rivalry with Moka for Tsukune’s affection.