Chigusa Iino serves as the nurse and science teacher for female students attending a one-month co-ed trial at Kanenone Gakuen from their all-girls boarding school. She supervises the girls, manages their physical and emotional well-being, and ensures their safety during this integration program.

Standing 170 cm tall, she has a slim build, a pale complexion, short brown hair in a bob cut, and brown eyes. Her professional attire typically combines a lab coat with a skirt, and she possesses a large bust.

Chigusa maintains a consistently carefree and easy-going demeanor. She actively encourages social interaction and romantic exploration between the students, adopting a lenient approach distinct from stricter faculty. She handles inappropriate or sexually charged behavior, especially from the Baka Trio's Bacchi-Gū, with composure, responding with a smile rather than punitive measures.

Outside of school duties, she occasionally drinks sake, often while coping with relationship struggles involving her boyfriend Yuji. Though she offers students guidance on interpersonal and romantic matters, she does not resolve her own relational challenges. Her role remains focused on facilitating student interactions during the co-ed trial.