(W/A/CA) Sakae Saito Youko gets a message from her sister, sending Airi and her off to Tsukuba, a city of research and universities. Then, after a stop to stretch their legs at Lake Kasumigaura, the two find themselves at Motegi Mobility Resort-a motorsport mecca with tons of well-preserved bikes!

(W/A) Sakae Saito Youko and Airi's next stop is Umihotaru, a rest stop in the middle of Tokyo Bay famous for its nighttime view. But with the Aqua-line tunnel from Kawasaki flooded, they're forced to take a huge detour all the way to Chiba. On the way, they make a stop in Akihabara to investigate a mysterious radio signal. Could someone still be alive there??