Neppuu (a Touhou LW original) refers to a hot, dry wind. This is an apt temperament for Reisen, the moon rabbit in a nurse uniform seeking to protect everyone's physical and mental health at the end of summer. "All moon rabbits should have wings!" (Strong against Wood Phase.) "On Earth, I'm the head nurse. Isn't that right, Lady Sagume?" (Strong against Earth Phase.) "Summer flu, exhaustion, heat stroke... I'll heal 'em all!" (Strong against Star Essence.) "Phew... I never realized being a nurse was such hard work." (Weak to Fire Phase.)

The ability of Reisen Udongein Inaba from the world obsessed with healers (a Touhou LW original). This ability doesn't seem that different from the Reisen of our world's ability. In Reisen's world, medical care takes the form of a battle of bullets. They call it "playing doctor," but long ago, medicine and ritual were the same thing, with both containing extraordinary knowledge needed for survival. There were strange tools, cryptic chants, and mysterious ingredients burned, crushed, mixed, and brewed. The Japanese word for a quack doctor, "yabu," was once used to refer to shrine maidens who also practiced medicine―with the doctor who keeps her clinic deep in a bamboo grove being a prime example of a yabu. One day, Eirin Yagokoro noticed something unusual. "Hm? Reisen... there's something on your back." The wings growing from Reisen's back became larger by the day, and before long, a halo-like ring appeared above her head. Eirin documented the changes in detail. At first, Reisen felt like crying all the time. But her one saving grace was that these unnatural objects could be hidden or summoned at will. Eirin quickly deduced that Reisen was using her ability to manipulate wavelength to cancel out their phase and render them invisible. Using that ability as a reference, Eirin developed a new medicine and sent it to her disciples in the Lunar Capital, where rumors of "Wing Syndrome" had begun to spread. Suddenly growing wings is unlikely to go unnoticed. Those afflicted might not even want to leave their homes. Medicine isn't just about physical health―it also extends to the mind and one's social well-being. Interdimensional benign tumors manifesting behind the back and above the head... These structures aren't attached to the body, yet they move together with it, as if their relative coordinates are fixed. Though called "benign tumors," they may in fact be parasitic lifeforms... from another dimension. One reason to think they are parasitic is that they grant their host an immense wealth of medical knowledge and skills, meaning that they exert influence on their host's memory and physical abilities. Ordinarily, parasitic organisms inhibit their host's abilities, but some form mutualistic relationships that benefit both host and parasite. Though these seem like opposing outcomes, it's ultimately just a matter of what benefits the parasite the most. For some reason, this particular parasite benefits most when its host is well-versed in medicine. Eirin vaguely recalled a science fiction novel from the outside world she once read. It, too, featured parasitic beings that bestowed knowledge. Perhaps it wasn't such an unusual concept after all. Reisen's parasite came to be known as "Astral Door." It was a living singularity. A sentient gate. A mobile portal. A friendly wormhole. A door to the peak of summer. "As above, so below; as below, so above." Perhaps it was the embodiment of a fantastical law that bound the heavens and the Earth, a relic from the era when medicine and alchemy were one and the same. It allowed for secret medicine stored in other dimensions to be extracted, like unearthing OOPArts (out-of-place artifacts) from the soil. To Eirin, the Brain of the Moon, Astral Door didn't tell her anything she didn't already know. But it proved useful as a stable and cost-effective living biofactory. For her research conducted on Reisen and Astral Door, Eirin was later awarded the Eirin Prize for Physiology and Medicine by the sages of the Lunar Capital, a prize she herself had founded... But for her, such things were trivial. Around the same time Astral Door appeared, the world's climate began to shift towards the peak of summer. Normally, that's when people start paying attention to their health, and when their craving for grilled eel takes hold. If you absorb too much summer heat, your body loses its balance of temperaments, making you more prone to illness. Astral Door and the peak of summer arrived at the same time... Was it a mere coincidence? One thing is certain: this world favors health enthusiasts. "I wonder what the sages of Gensokyo think about medical treatment turning into a battle of bullets," Reisen muttered to a colleague, reflecting on how her new wings and halo and the warming climate were probably less the fault of nature and more the work of her master. "I don't EVER know what those sages are thinking," replied Tewi Inaba as she stared at Reisen's angelic form, noting how Astral Door resembled the luminous structures some people manifest behind them during battles of bullets. When you’ve lived a long life, you start developing an instinct for what's going on in other people's heads. "There are plenty of medical pros here on the surface, too, you know?" "Medical pros? You mean like gods? I didn't know there were any famous ones here." "Seriously? Iizuna Gongen has been known to heal people. And Sukunahikona makes medicine..." Then, with a smug grin, Tewi said, "But the real big name? Lord Daikoku!"