In 2011, Japan experienced a huge earthquake followed by a tsunami and a nuclear power accident known as the Great East Japan Earthquake (GEJE). This chapter focuses on impacts of the tsunami and the reconstruction of coastal zones affected by GEJE, with a greater emphasis on sea wall reconstruction. The main question addressed in this chapter is how ecosystems played and are playing a role in GEJE and the reconstruction process from both policy and implementation perspectives. In this respect, it reviews how sea walls, coastal forests, traditional knowledge and protected areas played out during the GEJE. The chapter also provides a review of policy responses after GEJE to promote ecosystem-based disaster risk reduction (Eco-DRR) both at the global as well as national level by the government of Japan. It then reviews reconstruction activities on the ground with a particular focus on coastal areas such as reconstruction of sea walls and coastal forest. Finally, policy-implementation gaps and lessons are discussed from an Eco-DRR point of view based on these practical experiences.