Banri Shiroishi is a first-year business student and the drummer for Argonavis. Despite his relatively small frame at 165 cm and 51 kg, he delivers powerful drumming honed since childhood through taiko practice. His pragmatic focus on finances stems from his family's struggling dairy farm, burdened by significant debt; he aims to rebuild it through music, leading to waste-averse, stingy tendencies without greed.

Yet, Banri consistently energizes the band as a high-energy mood maker, often pushing Argonavis to seize opportunities and exceed limits. Personality analyses suggest an ESTJ type and Enneagram 9w1, highlighting his empathy, desire for group harmony, and role as a mediator. This peacekeeping can sometimes result in passive-aggressive behavior or difficulty asserting his own opinions and setting boundaries.

Within Argonavis, Banri contributes significantly beyond drumming, boosting morale and influencing decision-making. His unique blend of practical financial drive and enthusiastic support makes him a driving force in both the logistical and emotional aspects of the band.