Chako Hasegawa attends East Oizumi Academy as a high school student and belongs to the Cosplay Association club. She sports pink hair in a ponytail secured by a hairband, green eyes, and typically dons her plaid-design school uniform bearing the school crest. Having moved from her family home, she now resides with Sachiko Arii, a widow.

Chako radiates exuberance, cheerfulness, and high energy, frequently peppering conversations with self-coined phrases like "Have a Chako-riffic day" and "Let's give it the old CHAKO TRY." Her enthusiasm for cosplay clashes with chronic clumsiness and forgetfulness, often leading to damaged costumes or forgotten event supplies. These mishaps require regular intervention from Delmo, a magical bunnygirl companion who conjures costumes or alters appearances in exchange for food.

As the club's designated "Ace" cosplayer, Chako passionately pursues their goal to compete in the Cosplay World Series. Her cosplay abilities prove inconsistent; she falters at crafting costumes yet delivers standout stage portrayals like Street Fighter's Chun-Li or references to Sakura Kinomoto and Princess Serenity. Occasional insecurity surfaces about her physical appearance, particularly her small bust size relative to fellow club members.

Her primary romantic subplot involves Kousuke Tamiya, a college photography enthusiast who declares himself her biggest fan. His admiration fuels her drive, though their relationship remains limited in development. In her leadership capacity, Chako rallies clubmates, notably aiding the shy Tsukasa Tomii from a rival club to conquer stage fright.