Aoi Sakamoto is the wife of the protagonist Taro Sakamoto and a central figure in his transformation from a legendary hitman to a peaceful convenience store owner. Her background begins when she was working as a cashier at a convenience store, where Sakamoto fell in love with her at first sight. This encounter was the catalyst that led him to abandon his violent profession and pursue a normal life.

In terms of personality, Aoi is a loving and caring woman who exudes warmth and a serene demeanor. She is the emotional cornerstone of her family and brings a sense of normalcy and joy to her husband's life. However, beneath her gentle exterior lies an individual of immense resolve and unwavering principles. She possesses nerves of steel and remains composed even in dangerous situations, trusting completely in her husband's abilities. When angered or when her strict moral code is challenged, she can display a forceful and intimidating presence that can awe even seasoned assassins. Her principles are so strict that she has established a set of family rules, with the most important being that Sakamoto must never take another life. She is also known to be somewhat of an extremist, willing to go to great lengths to prove a point about her beliefs.

Aoi's primary motivation and role in the story is to serve as the moral compass and the reason for Sakamoto's new path. She holds him to his promise to use his skills to protect people rather than kill them, and she has made it clear that she would leave him if he ever returned to his old ways. She showed Sakamoto through a dramatic act, throwing herself from a balcony on Christmas Eve, the pain of losing someone precious and made him promise to atone for his past by helping others. Her role is not as a fighter but as the heart of the Sakamoto household and the manager of their daily lives, adept with numbers and keeping both the household and their convenience store running smoothly.

Key relationships define her character. Her bond with her husband Taro is the foundation of the entire series, as he is so devoted to her that he abandoned his legendary status as an assassin. She is also the mother of their daughter, Hana Sakamoto, and together they form a small, loving family. Her relationship with her husband's former associates, such as the psychic Shin, is built on the respect they have for the peaceful life she has given Sakamoto.

Regarding development, Aoi's most significant arc occurs before the main story begins. She evolved from a convenience store cashier who fell in love with a feared killer into the woman who reformed him. She forced him to confront the value of human life and transformed a ruthless hitman into a devoted husband and father. Throughout the main narrative, she remains a static yet powerful force for good, representing the normal world that Sakamoto fights to protect.

While Aoi Sakamoto does not possess superhuman combat abilities like her husband, her notable abilities are psychological and domestic. Her greatest strength is her unshakable mental fortitude and charisma, which command respect from even the toughest ex-assassins. She is a skilled manager who keeps the family business and household in perfect order. She also has a playful hobby of performing magic tricks, which offers a gentle contrast to her occasionally intimidating aura and her husband's violent past.