This article describes the story of Imperishable Night in detail.
The youkai of Gensokyo notice that a small sliver of the full moon is missing. Although humans wouldn't realize the difference, the youkai are extremely troubled by it. Yukari, Alice, Remilia, and Yuyuko enlist Reimu, Marisa, Sakuya, and Youmu to help get to the bottom of the latest incident. This time, the girls pair up as follows: Yukari and Reimu (Barrier Team), Alice and Marisa (Magic Team), Remilia and Sakuya (Scarlet Team), or Yuyuko and Youmu (Netherworld Team). Only one of these teams actually goes out and resolves the incident. To buy time, the team causes a never-ending night.
- This game is Curtain Fire Shooting Game.
- Girls do their best now and are preparing. Please watch warmly until it is ready.
- Paradisiac moon was broken! This incident is unprecedented serious affair.
- Barrier Team's Scenario (Reimu Hakurei & Yukari Yakumo)
- Magic Team's Scenario (Marisa Kirisame & Alice Margatroid)
- Scarlet Team's Scenario (Remilia Scarlet & Sakuya Izayoi)
- Netherworld Team's Scenario (Youmu Konpaku & Yuyuko Saigyouji)
A human and youkai team set off along a forest path to investigate. Along the way, they encounter firefly youkai Wriggle Nightbug and night sparrow youkai Mystia Lorelei, both of whom are quickly defeated. As they approach the Human Village, they meet half-beast Keine Kamishirasawa, who is protecting the village from youkai. She mistakes the team for enemies and attacks them. After the team defeats her, Keine indicates that the person who switched the moons is in the Bamboo Forest of the Lost. In the bamboo forest, they encounter either Reimu (if the player is the Magic Team or the Scarlet Team) or Marisa (if the player is the Barrier Team or the Netherworld Team); both of them demand to know why the team has been freezing time and causing an imperishable night.
Finally the team reaches the eternal mansion Eientei. Once inside, they find that the mansion is guarded by numerous rabbits, including Tewi Inaba and Reisen Udongein Inaba, who uses her powers to disorient the team. Confused, the team must choose which path to take; one leads to the real moon and the other leads to the fake moon. If they pick the path leading to the fake moon, the team gets to fight the person who created the fake moon, Eirin Yagokoro. Eirin reveals she sealed the earth from the moon to prevent the Lunarians from taking her mistress, moon princess Kaguya Houraisan, and that she created a fake moon to prevent everyone else from noticing. If the team picks the path leading to the real moon, they are able to meet Kaguya herself. Tired of hiding from the lunar emissaries, Kaguya challenges them to face the "5 impossible requests."
- Bad endings
Barrier Team's has them return to the shrine in the morning with Yukari vanishing off until the evening with Reimu resigning herself to Yukari's tendencies and trying again the next night.
Magic team's has Alice sleep over at Marisa's upon returning with Marisa vowing to succeed next time as Alice dreams of a successful resolution.
Scarlet team's has Remilia being upset but going to sleep with Sakuya talking about trying again and how she needs rest as well. The ending notes no one knows how Sakuya rests and how her job is endless.
Netherworld Team's has them returning where Yuyuko went right to sleep with Youmu talking about Yuyuko's seemingly bad mood. It mentions that Youmu is considering a vacation and that Yuyuko fell asleep due to the long night wearing on her.
- Normal endings
Barrier Team's has Reimu, Marisa, Alice, Yukari, Ran, and Chen relaxing at the shrine where they talk about the moon, how to drink sake on a full moon, its powers and it ends with the hint that things aren't really settled.
Magic team's has Marisa and Alice visit to the shrine to look at the moon to find it's still abnormal. They notice Reimu not even being home (perhaps hinting at Reimu departing to resolve things?). It mentions how the seemingly full moon hasn't waned in days and that they would have to try again.
Scarlet team's has them at the mansion talking about how the Moon's been quite red as of late and Remilia voiced her annoyance at how unusual it is. They suspect it's due to Reisen as they talk about chasing her down again.
Netherworld Team's has them at their home talking about a festival and pickled vegetables as Yuyuko then goes about making Youmu prepare some. After a bit of pestering Youmu gives it. It ends with noting the fake moon is still out and that they would have another trip.
- Good endings
Barrier Team's is similar to the normal endings, but their discussion is about the real full moon, how it might be giving Ran human traits and Ran joking about Chen's wrath as the younger girl appears drunk. They're surprised by Eirin, Kaguya and Reisen visiting as they talk about the barrier preventing any messengers from the moons from entering, Kaguya's past of hiding on earth, and Kaguya stating how a moment of fun is worth more than thousand of years of boring living as it goes on to have Eirin and Kaguya mooch food from Reimu and Reisen respectively and Marisa joking about their not being from the moon. It goes on to say the fake moon put Gensokyo's balance at risk and that part of rebalancing is considering the Lunarians half humans.
Magic Team's has Marisa and Alice visit Eientei, bickering some. Reisen pops up asking what they want with their visit, accusing them of sneaking about, with some talk about what Marisa really is with Marisa saying outright that she's a thief. Alice then suggests asking about an appointment but noting it'd be too late for that. Kaguya appears and forces Reisen to serve them tea and snacks as she talks about how things have changed on earth as Marisa and Alice bicker some more, which only amuses Kaguya. It notes that while the Lunarians usually shun visitors, but with people like the two magicians, they have no choice but to get to know them.
Scarlet Team's starts with Sakuya in the mansion pondering what to do after the incident, remarking on a meeting that might involve going to the moon (SSiB forshadowing?). Remilia appears who talks about japanese food and how humans have already been on the moon, and Sakuya being with youkai so long she can't be called human. Remilia then proceeds with talk of going to the moon as she asks Patchouli to join in the planning, all the while Sakuya is baffled by what the require for the plan (An engine, something to convert things to the energy need and a 1000 people's worth of blood) with the last one, Armstrong completely baffling her. It notes that while the notion was impossible, Remilia and Patchouli would not let go of it and Sakuya concluding everyone one else had gone mad.
Netherworld Team's has Eirin visiting Hakugyokurou as Yuyuko serves Tea that turns out to be poisonous as Eirin recognizes the ingredient and notes with her expertise that poisoning attempts won't work on her. Yuyuko hints at not using all her power and wonders about giving the rest to Youmu. Yuyuko reveals that after seeing the true moon both her and Youmu's eyes have been hurting and that she attempted to poison Eirin as to get her services for them permanently. Eirin answers she can't fix that problem but she will attend to other problems in the future. They talk about the death and Netherworld, or precisely the oddity of a ghost worrying about her health. Youmu comes in talking about a holy living spirit and Eirin realizing she's gotten case of insanity. She offers some therapy before making a medicine as she goes on to say she can't work for them directly as she drank the "medicine made with the princess' ability" (better known as the Hourai Elixir), which Yuyuko calls her greatest enemy. Youmu wonders about who'd want to make enemies with Yuyuko. Yuyuko then tells Youmu not to drink the tea as Eirin remarks on different treatments. It goes on to state that Yuyuko considers the hourai elixir-immortals her enemies as the elixir prevents death which in turn prevents new ghosts from arriving in the Netherworld, making it less "lively".
Shortly after the events of the main story, Reimu, Marisa, Sakuya, and Youmu were hanging out at the Hakurei shrine. They were bored when Kaguya appears and challenges them to partake in a "trial of guts" at the bamboo forest on the night of the full moon. Kaguya also insists they pair up with the same partners as before. So the girls set out at midnight, uncertain of Kaguya's real intention behind her request.
- Extra Start mode unlocked!
- Continue the dream a little further...
While going through the bamboo forest, the team encounters Keine, now in hakutaku form. Keine tries to stop them from reaching "that human", but the team proceeds to defeat her. Shortly afterwards, the team meets said human, Fujiwara no Mokou. Mokou reveals she is immortal like Kaguya and consumed the Hourai Elixir. When Mokou finds out that it was Kaguya who ordered them to take the trial of guts, she realizes Kaguya actually sent them to assassinate her and attacks the team. Once Mokou is defeated, the team has the opportunity to consume some of Mokou's flesh to complete the trial of guts, but they decide against that. (It's mentioned that whoever eats the flesh of an immortal gains eternal life, but the humans didn't want to eat another human's guts, presumably since eating humans is what youkai would do.)