In Japan, various styles of Lesson Study (LS) have been born over 140 years. The first issue is what should be the focus of observation in the live lesson. There are two trends with regard to the target of observation. One is teacher- and lesson-plan-centered observation since the Meiji era (1870s), and the other is child-centered observation since the Taisho era (1910s). The former is closely related to administrative-led teacher training. The latter is more complex and can be further divided into five types. The second issue is which activities are given priority in the LS processes: observation of the live lesson itself, preparation before the lesson, or reflection after the lesson. Furthermore, each activity can be designed as a personal or a collaborative process. Thus, there are roughly six types of LS in Japan related to this issue. Which type is adopted depends on the period, lesson-study frequency, and school type. In addition, it is noteworthy that the type of LS implemented is closely related to which of demonstration teacher or observers are regarded as the central learners. The third issue is whether to regard LS as scientific research or as literary research. Teachers and researchers in 1960s Japan had strong interest in making lessons and lesson studies more scientific. On the other hand, as teachers attempt to become more scientific, they cannot but deny their daily practice: making improvised decisions on complicated situations without objective evidence. Although lesson studies have been revised in various forms and permutations over the last 140, formalization and ceremonialization of lesson studies has become such that many find lesson studies increasingly meaningless and burdensome. What has become clear through the discussions on the three issues, the factors that impede teacher learning in LS are summarized in the following four points; the bureaucracy controlled technical expert model, exclusion of things that are not considered scientific, the view of the individualistic learning model, and the school culture of totalitarian products. To overcome obstruction of teachers’ education in LS and the school crisis around the 1980s, the “innovative LS Cases” has begun in the 1990s. The innovative LS aims not for as many teachers as possible but for every teacher to learn at high quality. In the innovative LS Case, what teachers are trying to learn through methods of new LS is more important than methods of new LS itself. Although paradoxical, in order to assist every single teacher to engage in high quality learning inside school, LS is inadequate. It is essential that LS address not only how to actualize every single teacher to learn with high quality in LS but also through LS how to improve collegiality which enhances daily informal collaborative learning in teachers room. Furthermore, LS cannot be established as LS alone, and the school reform for designing a professional learning community is indispensable. Finally, the concept of “the lesson study of lesson study (LSLS)” for sustainable teacher professional development is proposed through organizing another professional learning communities among managers and researchers.