Sweet potatoes are a popular food throughout Japan. They're baked, simmered, added to soup, and turned into confectionery. Baked sweet potatoes are a beloved street food. Recently, sweet potatoes have also been used for purposes other than food. They've been planted on rooftops to keep buildings cool, and waste material from sweet potatoes has been fermented to produce methane for use in generating electricity. We introduce the increasingly diverse ways in which sweet potatoes are used and sold.

Many Japanese kitchens are now hyper-modern, but two or three centuries ago, most were basic spaces with dirt floors. One turning point came after the Second World War. Large apartment complexes built to address a housing shortage needed to be compact. For the first time, cooking and eating spaces were combined into one carefully designed "dining kitchen." Since then, kitchens have improved in both comfort and convenience. We introduce the ongoing evolution of the Japanese kitchen.

The waxing and waning moon. Throughout Japan's history, it has been loved, cherished and given many special names. Moon-viewing events are held across the country at the time of the beautiful harvest moon, which occurs during the eighth month of the traditional calendar. And the moon's gravitational pull has long been important in agriculture and fishing. We introduce Japan's aesthetic appreciation of the moon and look at some new technology being developed for use on the lunar surface itself.

Frozen food is extremely popular in Japan. A supermarket may have a dedicated section with hundreds of frozen items. While pasta is the most popular frozen food, options range from chopped vegetables to sushi. One key to the success of frozen food is flash freezing, which limits damage to food cells during the freezing process, thus preserving taste and texture. Flash freezing is a great way to make food last longer. We review the history of Japanese frozen food and introduce recent innovations.

In recent years, a sense of nostalgia has been spreading among young people in Japan for the Showa era, which lasted from 1926 to 1989. A theme park has opened a recreation of a 1960s shopping street. Radio-cassette players and colorful retro designs are once again popular. And long-established cafes serve recipes that haven't changed in decades. We introduce some of the cultural elements defining an era that many Japanese people consider the "good old days."