Misono Arisuin is a fifteen year old boy and the youngest member of the wealthy Alicein household. He is the Eve of the seventh Servamp, Lust, whose contracted form is named Snow Lily. Misono is small and slender with a frail build, short dark purple hair parted at the center with a prominent strand sticking upward, and narrow purple eyes. Due to his weak constitution, he is easily exhausted and often relies on a throne-like chair called the Lead for support, even outside of combat. His birthday is February fourteenth, his blood type is A, and he enjoys chess, reading in his garden, and chocolate fondant, while he dislikes crowds.

Misono was born as the son of Mikado Alicein and Mikuni's teacher, who were involved in an affair. He was raised by his mother until she was murdered by Mikuni's mother out of jealousy. Mikuni's mother then raised Misono as her own son, and during that time he developed a close bond with his elder half-brother Mikuni. However, his stepmother's jealousy eventually led her to attempt to kill Misono. Mikuni intervened and killed his mother to protect him, and Misono entered the room just as the incident occurred, leaving him deeply traumatized. To shield him, Mikado ordered Snow Lily to erase Misono's memories of the event and manipulate his thoughts whenever he approached the east wing of the estate, where Mikuni had lived. Later, following the death of his grandfather, Misono encountered the Servamp of Lust, then known as All of Love, wandering alone in the family garden. He offered the old pocket watch he had inherited from his grandfather, renamed the Servamp Snow Lily, and formed a contract, making Lily his protector and partner. Because of his frail health, Misono spent most of his childhood confined to the Alicein villa, educated privately by a tutor named Hattori. He eventually attended a private school, but his poor constitution and sheltered upbringing prevented him from forming friendships during those early years.

At first impression, Misono comes across as arrogant, impolite, and distant. This behavior conceals a genuinely kind and caring nature. He values his friendships deeply and is particularly close to Mahiru Shirota, whom he regards as his first true friend. Despite his aloof manner, he is deeply concerned for the safety and well-being of those he cares about. He is physically frail and sensitive about his health and height, and he dislikes being in a position where others must protect him, aspiring instead to become stronger so that he can protect those around him. He is stubborn by nature and tends to push for his own way. Although he wishes to be seen as mature, many aspects of his upbringing have left him childish. His father, Mikado, continues to shelter him, enforcing strict routines such as early bedtimes and preserving childlike beliefs, including faith in Santa Claus. This overprotection has contributed to his immaturity and his fear of simple things such as the dark, snow, or bubbles in his eyes. Having grown up without friends, he never learned common games and often pretends to already know the rules rather than admit his ignorance. In his early childhood, he was described as cheerful and friendly, but after the trauma involving his brother, he began referring to Mikuni with hostility.

Misono is motivated by a desire to become strong enough to protect the people he cares about and to no longer be a burden on others. He feels ashamed of his inability to protect those close to him, which drives him to push himself despite his physical limitations. His role in the story is that of a supporting ally who provides strategic planning and combat support, using his intellect to analyze situations and coordinate with his allies. He is a key figure in the fight against the antagonistic Tsubaki and his group, and his partnership with Snow Lily is central to his contributions in battle.

His key relationships include his bond with Snow Lily, who serves as his protector and the instrument of his combat ability. He shares a close friendship with Mahiru Shirota, which begins on antagonistic terms when Misono demands that Mahiru hand over his Servamp, Kuro. Their conflict eventually gives way to an alliance, and their friendship develops as Mahiru offers to introduce Misono to his friends and exchange contact information. Over time, Misono grows genuinely concerned for Mahiru's safety, scolding him for reckless behavior and feeling ashamed of his inability to protect him. Their relationship reveals Misono's more vulnerable side. He also has a friendly relationship with Tetsu Sendagaya, marked by lighthearted bickering, particularly when Tetsu calls him shortie instead of big bro. Despite the teasing, Tetsu respects Misono's reasoning and planning abilities, often entrusting him with decision-making even in dangerous situations. Misono's relationship with his elder half-brother Mikuni is complicated by the altered memories of their past, leading him to initially refer to Mikuni with hostility, though some awareness of his brother's existence remains.

Throughout the series, Misono undergoes significant development. He grows from a lonely, isolated, and arrogant boy into someone who opens up to others, learns to trust and depend on his friends, and becomes more selfless, willing to put himself at risk for his allies. He confronts the truth about his past and his relationship with his brother, and he gradually learns to be more honest about his own vulnerabilities and desires.

Misono's primary ability as an Eve is the Execution Block of the Red Queen, which he activates in conjunction with Snow Lily. In battle, Misono and Lily flank their target before summoning the ability. Once activated, the opponent is forced into a chair and rendered immobile. Lily can then strike with his scythe, inflicting no physical harm on the body but dealing significant damage to the opponent's soul. Outside of combat, Misono frequently relies on his throne-like Lead for support due to his fragile constitution and low stamina.