Ryōko Mochizuki is a first-year student at Asaka Academy and a member of its rifle shooting club. She possesses long brown hair reaching her back and blue eyes. Her standard attire is the school uniform: a white short-sleeved collared button-up shirt tucked into a gray pleated skirt, paired with long white socks near her knees and laceless brown shoes.

Typically reserved, Ryōko displays confidence specifically when announcing competition lineups. She carefully observes others during practice sessions and shows consideration, stating she wouldn't want to disrupt fellow competitors' concentration.

Her activities include participating in a practice competition against Hikari Kokura and members of the Chidori High rifle club. During these events and club activities, she is consistently seen alongside fellow first-year Karen Sakashita. She is also acquainted with Akira Shinonome, the club president, and Misa Kuroi, the vice president.