Touring After the Apocalypse

As they recharge their battery-powered motorcycle, Youko and Airi explore the cafe at the Hakone Taikanzan. Airi later finds the wreck of a Maneuver Combat Vehicle and a nearby support truck containing rations. As they rest for some time, Airi notices that the MCV's sensors are actually watching them, when it suddenly springs back to life and attacks them. Airi disables the MCV using her arm-mounted plasma cannon, then Youko permanently shuts its AI off. They later take a side trip to Hakone's hot springs, where Youko had flashbacks of their trips to Hakone with her big sister, before heading to Yokohama Minatomirai next.

Youko and Airi travel toward the now-submerged Yokohama Minatomirai but are stopped by the broken Yokohama Bay Bridge. As Youko goes fishing, Airi discovers the upper half of a cyborg named Schwar, who reactivates when connected to their motorcycle's battery. Carrying a photo of his family, Schwar slowly regains his memories as they journey toward Yokosuka. Along the way, they encounter the wreck of a Sōryū-class submarine perched on the road and witness mutated giant orcas. Moved by the sight of the family of orcas, Schwar—whose real name is Ichiro Suzuki, a sailor with the Maritime Self-Defense Force—feels sorrow for never returning to his loved ones. Though Youko invites him to join them, he chooses to stay behind. As his batteries run out, Ichiro reflects on his past and the day meteors devastated Earth, finally sinking into the sea near Yokosuka—his final homecoming.

As Youko and Airi charge their motorcycle just outside Tokyo, they obtain much-needed fresh water from a river and discover canned goods hidden in one home and stayed overnight, where Youko found, and left alone, the remains of its former occupants--a married couple--lying in bed. They reach the partly-submerged Tokyo Big Sight the next day by following the ruined Yurikamome railway. Youko hoped to see motorcycles once exhibited there—especially those from a photo with her older sister at an annual motorcycle show—but find only remnants of doujin manga from the last event. Reading one, she feels the passion of its creator. As they rest after swimming with penguins in the nearby sea, Youko dreams of the world before the apocalypse—riding a gasoline-powered version of her motorcycle with her big sister. Upon waking, Airi hears distant music, which Youko hears by tuning her phone's radio app to the frequency of a FM station still transmitting from somewhere in the ruins of Akihabara, and thinks there are still others alive.

Youko and Airi trace the FM broadcast to its source, hoping to find surviving humans. Their search leads them to a cosplay cafe and an Akihabara overrun by descendants of animals that escaped from Ueno Zoo. After narrowly avoiding danger, they reach the building housing the radio station. Inside the broadcast room, amidst music, they discover a solar-powered computer running the station automatically by its AI, DJ Akiba Jiro II. It could "see" and "hear" through a web camera, but cannot hold full conversations. Notes left by its creator, DJ Akiba Taro, as well as a box of manuals and parts reveal he rigged the station's computer and programmed the AI to allow it to continue broadcasting even after humanity's fall. When the AI shuts down at sunset, Youko and Airi spend the night repairing and upgrading the station with scavenged parts, adding a speaker system. DJ Akiba Jiro II reactivates the next morning, and reads their message encouraging it to “keep delivering music to the world,” and plays their requested song—based on a nursery rhyme by Takashi Yanase—as they leave Akihabara.

While traveling through the swampy ruins of the highway somewhere in Chiba toward Umihotaru, Youko and Airi hit a muddy patch and decide to camp overnight to clean themselves and their motorcycle. Youko briefly considers returning to the shelter for repairs but chooses to continue their journey, eager to see more of the world. While the two are fishing for dinner, Youko notices the wind dying down, fish fleeing, and spotting the unnaturally large full moon. The next day, with Youko still drowsy and unsettled by the night's strange calm, they ride on, with Airi seeing the moon as a bad omen. Their worries deepen when they suffer their first tire puncture and encounter a supercell. They finally reach the remnants of the Tokyo Bay Aqua-Line leading to Umihotaru Island. Youko experiences fear—and the thrill that comes with it—for the first time as they passed through a bridge crossing Tokyo Bay in stormy weather. The two take refuge at the station at Umihotaru, unaware that unseen eyes are watching them.

Sheltering from the storm at Umihotaru, Youko dreams of her times at Chiba with her sister—sharing food, the vending machines, and Tokyo’s night view. Exploring their location afterward, she and Airi find familiar spots from that dream and discover the “eyes” watching them were rats. Trying to fend their attacks off, they accidentally drop their fire torch, igniting leaking fuel, causing an explosion that kills the rats and blows the duo clear of Umihotaru. Safe but shaken, Youko realizes the harsh reality of the world's dangers and cruelties hiding beneath their seemingly carefree travels. That night, they witness glowing blue waters caused by ostracods and lightning illuminating the shadowed ruins of Tokyo’s skyline. Youko photographs the sight out of awe.

An email from her sister arrives, coinciding with Airi suddenly freezing. The message mentions of a system glitch affecting the AI-Re06 android model, Airi's own. Though not serious, it is fixable only at a research lab in Tsukuba. The next morning, as they do laundry, Airi reminds Youko to care for herself. After ringing the Bell of Happiness, they set out for Tsukuba.

Youko and Airi stop at the National Motorcycle Shrine before heading to Tsukuba. After a wrong turn, they find the research lab—whose entrance is a payphone beside a full-scale H-II rocket model—and descend into an underground facility where automated instructions guide Airi’s maintenance and Youko’s health check. When they exit, Airi’s glitch is fixed, and she has gathered space food and an astronaut helmet from a nearby building. Their Touringram app updates with GPS tagging and an offline stamp rally tied to places Youko’s sister once visited. They spend the night at the ruins of the Tsukuba Expo Center Planetarium, wondering if more research facilities—and perhaps more people—might still exist, even in space. Their next destination is the closest marked location: Kasumigaura.

At Lake Kasumigaura, Youko and Airi hunt ducks, gather lotus roots, and playfully wrestle in the mud before exploring a nearby observation tower. There, they test Touringram’s offline stamp rally, which works even without internet. At the Mobility Resort Motegi, their next stop, Youko wants to ride the still-intact Twin Ring circuit but waits to charge their motorcycle. Exploring the place and collecting their next digital stamp in the meantime, Youko briefly hears phantom engines on the start-finish line. Camping overnight, they see fireflies, prompting Airi to ask about the idea of a “soul,” which triggers memories of Youko’s past at the track. The next day, with the battery full, Youko runs the circuit at full speed, wearing a helmet Airi found in the paddock—mirroring her sister’s ride years before. Airi waves a checkered flag at the finish, and the two ride the course together.

After finishing their run at Twin Ring Motegi, Youko hears voices that lead her and Airi to the Honda Collection Hall. They restore power to the building and awaken ISAAQ, a maintenance robot who guides them through the vast collection of historic machines—from early Hondas to famous 500cc Grand Prix bikes and Formula 1 cars. When Youko asks if any people remain, ISAAQ confirms there are none.

Youko dreams of riding the bike on the track, and by noon the #46 bike she wanted to ride is waiting for her. She rides while Airi remotely drives a sports car, and ISAAQ becomes overwhelmed by memories of the racetrack’s former glory. Youko briefly sees the “spirits” of the vehicles racing alongside them and thanking them, nearly causing her to crash.

Back in the pits, they realize only Youko witnessed these visions—and ISAAQ has stood unresponsive, finding out he's been in rough shape from the start, with the other robots being merely inert. Later that night, they see strange lights drifting in the air, leading Youko to wonder if machines and places might have “souls” too, and whether those unseen presences helped make her dream momentarily real.

Youko and Airi arrive at the Oarai ferry terminal, only to find it submerged. Youko dreams of boarding a ferry to Hokkaido with her sister, inspiring thoughts of continuing their journey north. Airi suggests using the highway instead, while stopping at sights along the way.

At the Oya History Museum, they search the cold underground halls for their next stamp, finally spotting the QR code on the ceiling while avoiding areas with human remains. They later visit the Kameiwa “Benkei Sword-Split Rock,” narrowly avoiding being crushed when a boulder collapses.

Taking the steep Nikko Irohazaka road, Youko nearly loses control from excitement but makes it to the summit. At Kegon Falls, they slip through an emergency route to the viewing deck, where the stunning sight leaves them silent—Youko moved to tears.

While fishing at Lake Chuzenji, Airi hears a brief high-pitched sound. After visiting Senjogahara and the Nikko Toshogu Shrine, she urges Youko to head toward the place where she heard it. From the tri-boundary of Gunma, Saitama, and Tochigi, they follow the sound to the Yoshimi Hundred Caves, where they find glowing moss and camp overnight.

While Youko sleeps, Airi follows the sound and, discovering a cat, encounters a blinding flash and a dark, shifting object. When the cat disappears into it, Airi is pulled in as well and transported to outer space, where an unseen presence communicates with her and shows Earth in the distant past.

Airi later reappears near the caves and reunites with Youko, explaining that she encountered an alien teleportation device and that the Hundred Caves were built by humans and aliens 1,500 years ago. The beings, unable to communicate directly and having waited too long, believe civilization is still evolving. To answer them, Youko rides her motorcycle up the cave stairs, symbolizing humanity’s progress. The aliens respond as a bright light, leaving a final message: to meet again at the same place in 100 years.