Under cover of darkness, moving by stealth, ninja used superb physical skill and special equipment to infiltrate and disrupt their enemies. Ninja appeared during Japan's age of regional conflict, and their origins seem to lie in small communities that were clustered in the mountainous regions of Iga and Koka. Our expert guest this time is Hiroshi Ikeda, who has spent the last 25 years tracking down information about ninja.

Japan's castles are masterworks of wood and stone. They bristled with defences and functioned as symbols of authority. Today they are cherished local landmarks and popular tourist spots. With their architectural elegance and ingenious fortification, castles have long played a prominent role in Japan. Our expert guest this time is Yoshihiro Senda, the president of Nara University and an archaeologist who specializes in castles.