This study practically clarifies the inner transformation of mentees on how, through mentoring, young Japanese history teachers perceive their subject and how they attempt to improve their lessons based on their perceptions. In doing so, the educational possibilities for currently working teachers, which is based on the teachers’ reflections on their perception of their subject, are elucidated. The results show that the gap between what was learned at university and practice in the field suggests the possibility of recovery in the “washed out” perspectives about their subject developed during their teacher-training period. As two mentees were mentored, they explored their perspectives about their subject and the ideal profile of a history teacher, by reflecting on their prior training and education. In addition, it is difficult for currently working teachers to “refresh” their perspectives about their subject. As well as the difficulty completing adult education, this result also suggests the importance of the teachers’ initial university studies. Consequently, it is vital to ensure continuity in the training and development of history teachers.