Sunny Milk, Luna Child and Star Sapphire are the Three Fairies of Light, a group of mischevious Nature Spirits who live in the Forest of Magic (and later, the grounds of the Hakurei Shrine). With boundless enthusiasm and childlike intelligence, they have a tendency to get in over their heads, though they will often encounter people who are willing to help them out... or punish them for their shenanigans. Reimu Hakurei and Marisa Kirisame, Player Characters of the main game series, serve as secondary protagonists.
Over the course of its run, Sangetsusei has been published under four subtitles:
- Eastern and Little Nature Deity (1 volume), illustrated by Nemu Matsukura and running in MediaMix Game Magazine. The Tankobon edition also includes the short story "Fairy of the Moon", featuring an encounter between Luna Child and Yukari Yakumo.
- Strange and Bright Nature Deity (3 volumes), also running in MediaMix Game Magazine, which switches the artist to Makoto Hirasaka due to Matsukura's health problems.
- Oriental Sacred Place (3 volumes), running in Comp Ace.
- Visionary Fairies in Shrine (3 volumes), a surprise return to the series after a four-year hiatus, which adds hell fairy Clownpiece from Touhou Kanjuden ~ Legacy of Lunatic Kingdom to the main cast.
Each volume of the manga comes with a short CD featuring music related to the characters.
Sangetsusei eventually received its own game, Yousei Daisensou ~ Touhou Sangetsusei, in which Cirno sets out to punish the Three Fairies of Light for destroying her igloo. Unusually the art for this game was drawn by Makoto Hirasaka rather than ZUN himself.
Touhou Sangetsusei provides examples of:
- Absentee Actor: Oddly enough, in Chapter 8 of Visionary Fairies in Shrine Reimu, Marisa, and Clownpiece don't appear at all, even as a cameo.
- Art Evolution: Visionary Fairies in Shrine moves away somewhat from the Puni Plush artstyle of earlier installments, with members of the cast looking noticably thinner than before. Its newer character designs also rely less on Only Six Faces - Mamizou for instance has distinctive long eyelashes similar to her Forbidden Scrollery appearance.
- Big Creepy-Crawlies: In Chapter 12 of Visionary Faries in Shrine the Forest of Magic is revealed to be home to giant rhinoceros and stag beetles, though none show up onscreen.
- Book-Ends: The last chapter of Oriental Sacred Place has the Three Fairies prank Reimu with a bomb hidden in snow. The first chapter of Visionary Fairies in Shrine begins with Reimu being left a bomb by the Fairies in the snow during the winter.
- Canon Immigrant: While they already existed in the same canon, Great Fairy Wars marks the first time that characters who debuted in the expanded material went on to appear in the games.
- Cargo Cult: Chapter 10 of Oriental Sacred Place features a radio tower from the Outside World appearing in the Forest of Magic, and the fairies' attempts to tap into its "communication powers".
- Chekhov's Lecture: The lecture on how fairies can be prayed to like harvest deities in Chapter 2 of Visionary Fairies in Shrine proves relevant in Chapter 6 when the Fairies (plus Marisa) reenacting Hanasaka Jiisan manages to make the cherry blossoms at the Hakurei Shrine bloom.
- Continuity Nod:
- In chapter 2 of Visionary Fairies in Shrine Clownpiece mentions the crystallized soul blossom phenomenon that occurs in Hell during the spring that was first shown in Wild and Horned Hermit, while noting that she finds cherry blossoms far more beautiful.
- In Chapter 3 of Visionary Fairies in Shrine, when the Fairies wake up to find their home covered in vines, Luna notes that the situation seems very familar, referencing the time a tsuchinoko covered their original home in vines in Chapter 9 and 10 of Strange and Bright Nature Deity. However, due to the generally poor long-term memory of fairies, she doesn't quite put two and two together.
- In the second portion of Chapter 11 of Visionary Fairies in Shrine, Nitori mentions to Marisa that the kappa can control the flow of the Genbu Ravine, which is a reference to Chapter 46 of Forbidden Scrollery, where it's mentioned that the kappa protect the Human Village against flooding.
- In Chapter 13 of Visionary Fairies in Shrine Marisa has to remind Reimu about how stone cherries are formed from the crystallized souls of those unable to achieve nirvana, which was first revealed in Chapter 28 of Wild and Horned Hermit.
- Crossover: Kasen Ibaraki from Wild and Horned Hermit shows up in chapters 16 and 17 of Oriental Sacred Place, bringing some of the tone of her manga with her.
- Cross Through: Chapter 4 of Visionary Fairies in Shrine begins on roughly the same day as Chapter 45 of Forbidden Scrollery, and the typhoon that nearly killed Kosuzu is used by the Fairies to gather nuts, fruits, and mushrooms that were either knocked off their trees or started growing because of the storm.
- Curb-Stomp Battle: There's two examples of this:
- In the final chapter of Oriental Sacred Place the fairies challenge Reimu to a fight. The next panel is Reimu standing over their unconscious bodies.
- In the final chapter of Visionary Fairies in Shrine the fairies and Clownpiece are overwhelmed by Okina, who defeats all the fairies without getting a single scratch, even after the fairies get their second wind. Only Clownpiece is left as the last one standing, mainly due to the sacrifice of the other fairies, and by then, the battle's basically over.
- Death World: Clownpiece's descriptions of hell give off this vibe, especially in Chapter 4 of Visionary Fairies in Shrine, when she describes the typhoon from Forbidden Scrollery's "Let's Not Go Out on Purple Days" storyline as a mere pleasant breeze compared to the winds of hell, which can blow harder and longer.
- Defeat Means Friendship: Invoked. In the final chapter of Oriental Sacred Place the fairies try to improve their relationship with Reimu by attacking her, under the logic that Reimu always becomes friends with people after fighting them. It works.
- Early Installment Weirdness: Eastern and Little Nature Deity lasts only six chapters before a new artist is introduced, bringing a completely different art style.
- Epunymous Title: "Sangetsusei" can be translated very roughly as "three fairies", but "San-Getsu-Sei" is also homophonous with "Sun-Moon-Star".
- Facial Markings: The Bakedanuki that disguised herself as Marisa has a pair of small crescent shaped markings underneath her eyes.
- Field Power Effect: Sunny is at her strongest in sunlight, and can absorb it to heal her injuries. Luna has the same effect with moonlight, while Star is more or less the same at any time of day.
- Fisher King: Exploited by Yukari, who has the fairies move into a dead tree to bring it back to life. The tree in question was actually part of the Great Hakurei Barrier.
- Flashback: Clownpiece has a short one in Chapter 4 of Visionary Fairies in Shrine while remembering the conversation she had with Hecatia after being brought to live in Gensokyo by her.
- Foreshadowing: Chapter 6 of Visionary Fairies in Shrine shows that fairies are capable of altering the seasons if they get hyped up enough. The Bizarre Seasons from Hidden Star in Four Seasons turn out to be caused by fairies who were powered up en masse as a side-effect of the antagonists' plans and went berserk.
- Harmless Villains: The trio's ambition is to terrorise humankind and prove that fairies, like youkai, are not to be taken lightly. The most they manage is to mildly annoy people with their pranks.
- Hope Spot: During the finale of Visionary Fairies in Shrine, the fairies manage a Heroic Second Wind after their initial defeat by Okina. To add insult to injury, they defeat themselves through Okina's Deadly Dodging, and it's implied that was the case the first time as well.
- Man-Eating Plant: Chapter 12 of Visionary Fairies in Shrine reveals that the Forest of Magic is home to at least one man-eating morning glory, though it doesn't show up due to the lifeforce issues plaguing Gensokyo.
- Mundane Utility:
- In Chapter 4 of Oriental Sacred Place, Marisa uses a ghost-attracting gravestone to chill a watermelon for eating through their Ghostly Chill.
- Chapter 3 of Visionary Fairies in Shrine has Clownpiece's madness inducing torch being used to burn away the vines encasing the Three Fairies' home like a regular torch.
- Chapter 5 of Visionary Fairies in Shrine reveals that Reimu has been using Clownpiece's hellfire to keep the Shrine warm during the winter.
- Noodle Incident: Just what happened to make Sunny scared of Lily White?
- Our Gods Are Different: While fairies aren't actually gods, their nature as Nature Spirits makes them akin to divine spirits, and as a result harvest prayers directed at fairies work just as well as those aimed at actual deities.
- Power Nullifier: Reisen Udongein Inaba's abilities can cancel out all three of the fairies' powers. In addition Sunny's refraction powers allow her to easily tank most light-based attacks, even those used by Yukari Yakumo.
- Print Bonus: The Tankoubon of Eastern and Little Nature Deity contains a bonus prose work: Fairy of the Moon.
- The Rival: Cirno seems to see herself as such to the trio. Sometimes. Given the short attention span of fairies it's not very consistent.
- Sixth Ranger: Hell fairy Clownpiece from Legacy of Lunatic Kingdom becomes a recurring character and friend of the three fairies in Visionary Fairies in Shrine.
- Whole Plot Reference: In Chapter 6 of Visionary Fairies in Shrine, the Three Fairies and Clownpiece, assisted by Marisa, act out the tale of Hanasaka Jiisan in order to get the Hakurei Shrine's cherry blossoms to bloom.