Japanese sword is well known as a strong and sharp weapon and has a long history of more than 1000 years. The making process have not been well known especially for old swords (Koto) before Edo era since there were no written documents. Crystallographic or metallurgical characteristics are useful to understand the swords characteristics and consider the making process. However, studies to obtain such information have been not so easy since proper non-invasive methods were not popular. Neutron diffraction and imaging are powerful tool, and Bragg edge transmission imaging is a unique tool to obtain crystallographic information over a large area. Here, we introduce neutron methods and information obtained, and studies about Japanese swords.