Aoi Mizusawa is a central figure in the Monster Strike narrative, depicted across various media. She attends school with Ren Homura and ignites his involvement in Monster Strike battles by providing him with a specialized ring for monster control, positioning her as an experienced Striker before his arrival.

Her experience predates Ren's introduction, established in the side story Rain of Memories set one year earlier. She was part of an existing team with Haruma Kagutsuchi and Minami Wakaba. When Haruma proposes recruiting the vengeful Akira Kagetsuki—known for his violent combat style—Aoi expresses initial reservations but ultimately agrees based on trust in Haruma's judgment. This decision demonstrates her willingness to support teammates despite doubts. The team had deliberately reserved its fourth spot, indicating their selective approach to membership long before Ren joined.

Characterized by cheerfulness and positivity, Aoi shows notable growth from initial naivete to confident leadership, particularly in combat. Strategic thinking derived from gaming expertise proves essential, enabling her to coordinate team efforts against threats. Loyalty to teammates consistently motivates her commitment to protecting others.

Her combat abilities are linked to specific monsters, including Fox Metal the Legend and Napoleon the Valiant, reflecting her strategic approach, though detailed summoning mechanics remain unelaborated. Her surname Mizusawa combines "water" (水) and "marsh" (澤), while her given name Aoi (葵) refers to "hollyhock" or "althea".

Her narrative trajectory transitions her from an established team member to a mentor-like figure for newcomers. Her actions consistently emphasize group cohesion and mutual trust, evident in recruitment decisions and combat scenarios where her optimism counters darker motivations like Akira's initial quest for vengeance.