In Japan, the shortage of teachers has come to represent an important issue for educational administration in the 2020s. The causes of the teacher shortage are an increase in the number of retirees as a result of the age structure of teachers, and poor working conditions such as long working hours. In Japan, discussion continues about how to attract mid-career teachers into the teaching profession as a countermeasure against the teacher shortage. What is interesting about the situation in Japan is that lateral entry teachers are regarded as not only filling gaps in terms of quantity, but also as special beings who can bring a “Wind of Change” into schools. Japan’s teacher training system, which is remarkably lightweight by international standards, has been supplemented by collaborative improvement in schools after employment. Improvement presupposes that all of the teachers come to schools directly after graduating from a university. This system, which has prevailed historically, also imparts unique characteristics to the subject of lateral entry teachers. This chapter presents an examination of this topic using data from policy documents, a questionnaire survey of boards of education planned by the author, and interviews with lateral entry teachers.