Chiharu Andō is the younger sister of Mayuta Andō, ten years his junior. She attends the private Eihei Girls’ Academy Elementary Division and displays high academic ability, surpassing lower-middle high school students. Influenced by her brother, she adopted a delinquent mindset with rough speech and behavior, earning the nickname "Mad Dog," though she occasionally reveals a childish side. Chiharu greatly admires her brother. When Mayuta unexpectedly quits his biker gang, Hoshizorakai, and starts working legitimately, Chiharu becomes furious, viewing this change as uncool. She interrogates his former gang members and learns his reform was triggered by "a girl from Samejima Academy." This leads her to confront Chio Miyamo and Manana Nonomura in a "butt battle" to identify the responsible individual.

Chiharu habitually attempts to poke other people's buttocks. In her elementary school, this behavior is treated seriously, evolving into structured confrontations where cleaning duties are assigned based on the outcomes of formal butt-poking matches. Her approach is strategic and competitive. After losing the "butt battle" to Manana Nonomura, Chiharu admires Manana while becoming dismissive of Chio. Concurrently, she develops a rivalry with high school student Madoka Kushitori, captain of the Kabaddi Club, known for tactics like the "stripping Utsusemi technique" and engaging in sexual harassment. Madoka manipulates Chiharu into promoting Kabaddi, leveraging Chiharu's competitive nature and respect for structured contests.

Through involvement with Kabaddi, Chiharu reforms her delinquent tendencies and channels her energy into promoting the sport. She transitions from random butt-poking skirmishes to establishing a Kabaddi circle, actively recruiting former rivals, including those from earlier confrontations. This shift signifies her maturation as she moves from solitary antics to organizing group activities centered on a legitimate sport. Her efforts to formalize Kabaddi activities highlight her leadership potential and ability to inspire participation from former adversaries. Physically, Chiharu is characterized by girlish pigtails and a small stature fitting her elementary school age. Her journey progresses from a troublemaker fixated on her brother's legacy to a proactive promoter of a team sport.