Tsukinomori, Sayoko

月之森小夜子

A girl who travels with Bocca to seek her love, Kurofune. Her parents gave her as a sacrifice to monsters to improve her brother's chances of becoming a Monster Union agent. Kurofune rescued her, and she fell in love with him. She ran away from the home where Kurofune had placed her to chase after him. On her wrists, she wears the chains that bound her as a sacrifice; with them, she can track Kurofune. If she is lucky and nothing stands in the way of her and Kurofune, they will point to wherever he is. During the journey, Sayoko develops a relationship with Bocca.
Although her identity as a runaway child is the first facet of her character introduced to viewers, Sayoko is better known as a daring, sensitive girl ready to risk everything for love. She also possesses pickpocketing skills that rival a professional's, which helps her survive and leads her to Bocca. They later become friends when she realizes that Bocca is a Melos Warrior, and she decides to follow him so that she can look for Kurofune, whom she is in love with. Around Sayoko's left wrist is a red chain that vibrates and pulls her in the direction of Kurofune when he uses his power.
Bocca says that Sayoko is a “girl who belong to a world of sunlight”, but despite being generally cheerful in disposition, Sayoko’s past is marred by a dark truth. Her parents always loved her brother more than her. When her brother grew up, Sayoko was sacrificed to help her brother become a member of the Monster Union, and Kurofune saved her from it. That was when Sayoko fell for him. Together, Bocca and Sayoko traverse many monster-controlled areas, delving into the monsters' network and hierarchy. Amidst the conflicts and chaos, Bocca and Sayoko grow closer and find that their fondness for each other has developed into something more than friendship.