How can lesson study and learning study complement each other?

Lesson Study has a long history in Japan and has spread rapidly in the world in the past decade. Learning Study, a revised version of lesson study, has also witnessed rapid growth in some places like Hong Kong and Sweden. The paper analyzes the commonalities and differences of the two approaches and explores how the two approaches can complement each other. Case studies carried out in two secondary schools in Hong Kong and Singapore respectively are used to explore how Lesson Study and Learning Study complement each other.