Gakusha, a mouse distinguished by large glasses and a notably short tail, functions as the group's intellectual strategist. He employs practical knowledge and sharp problem-solving skills on their journey, with his expertise proving vital for overcoming obstacles—like building a new boat from salvaged scrap metal after their original vessel is destroyed.

A childhood friend of the sailor mouse captain Yoisho, Gakusha shares a deep, longstanding bond with him. This connection reinforces his role as a trusted advisor within the team. His analytical nature provides crucial balance against more impulsive characters during their mission to confront the weasel antagonist Noroi.

In the 2015 CG film adaptation, Gakusha maintains his core identity as a knowledgeable companion. He joins the expedition to defend Yumemishima Island against the Noroi Clan, continuing his narrative function as a thinker and planner. His contributions consistently focus on intellectual support and tactical assistance throughout the conflict.