The Seikan Tunnel, the world's longest undersea tunnel, connects the Japanese islands of Honshu and Hokkaido. Making it took 24 years, and the enormously challenging work claimed many lives. This time on Japanology Plus, we'll dig deep into the dedicated effort and technological know-how that helped to create the Seikan Tunnel. Our expert guest is Toshio Kadoya, who worked on construction of the tunnel for 18 years. And in Plus One, we look at a ferry service that predated the Seikan Tunnel.

At Japan's busiest airports, a flight may arrive or depart every two minutes or so. In spite of this, Japanese airlines are frequently ranked among the world's leading on-time flight operators. Making their punctual performance possible are Japanese values and professional expertise. This time on Japanology Plus, we explore the wonders of air travel in Japan. Our expert guest, Shunji Akimoto, is a journalist who covers the air industry globally. And in Plus One, how to wash a passenger jet.

This time on Japanology Plus, our theme is the Ogasawara Islands, a remote archipelago with a unique ecosystem and multicultural heritage. Located 1,000 kilometers off Japan's Pacific coast, the Ogasawara Islands were first settled by a group of Westerners and South Pacific Islanders, who interacted with later Japanese settlers to bring forth a unique culture. Our expert guide is Sho Sebori, a direct descendant of the American who became the leader of the first community on the islands.

Almost every primary school student in Japan uses the same type of school bag. These distinctive, blocky satchels are spacious, durable, and packed with clever features. This time on Japanology Plus, our theme is school satchels. We explore their history, production, and future potential. Our guest is Kuniyo Hayashi, the president of a long-established satchel-making company. And in Plus One, a primary school student shows us how she uses her bag on a day-to-day basis.

In Japan, the bath has a special status. And for Japanese, using one is an essential part of daily life. It's not just a place to wash yourself, but a chance to relax, reflect on your day, or spend time with your family. This time on Japanology Plus, our theme is bathrooms. Our guest is Osamu Oba, a professor at Kyoto Prefectural University. He explains why baths are so important in Japan, and introduces us to the latest innovations. And in Plus One, Matt Alt discovers how bath additives are created.

The Great East Japan Earthquake and tsunami left around 19,000 people dead or unaccounted for. It renewed Japan's sensitivity to the threat of natural disasters, and in the 10 years since then, a multitude of innovative emergency products and foods have been developed. This time, our theme is Emergency Goods. Our main guest, disaster mitigation advisor Kunizaki Nobue, introduces various useful items, and explains how Japan prepares for future catastrophes.

Japanese watches and clocks are respected around the world for their accuracy and durability. Many of them incorporate the latest technology. Our guest, Oda Ichiro, spent 26 years at a watchmaking company, and is now a university lecturer. He tells us the story of Japanese clockmaking, and introduces us to some clever and innovative timepieces. We also look at the incredible leaps in accuracy being made by cutting edge atomic clocks, and learn about the potential benefits of this technology.