Castle design evolved in 17th century Japan with stone walls as a key feature. Sakamoto in Shiga Prefecture became famous for its mason's expert techniques for dry-stacking. They traveled across Japan to complete their commissions. But when feudalism ended 150 years ago, many castles were destroyed. While most of the masons lost their jobs, one family in Sakamoto survived by refurbishing old ruins. But the 15th-generation master Suminori Awata is worried about the future. One day he receives an unexpected request to build a castle-style wall in Texas. Awata's journey begins.