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Touhou and Modern Science

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The Touhou Project series – while being primarily based on the religion known as Shinto – it is not unusual to see many functions of the Touhou world to rely on modern science (現代科学 gendaikagaku).

As ironic as it is, the god, Kanako Yasaka states in Wild and Horned Hermit chapter 2, "Nothing as unscientific as that is going to appear", to Reimu Hakurei's supernatural theories.

Nuclear Fusion as a Source of Green Energy

Kanako Yasaka and others stated that "nuclear fusion is green energy". Nuclear fusion is different from nuclear fission, with key advantages such as having criticality accidents not occur, and not releasing products as radioactive waste.[1]

There are several ways to achieve nuclear fusion. The most promising method being researched in the outside world is the deuterium-tritium reaction (or D-T reaction for short). While the easiest to achieve fusion with, it releases dangerous high-energy neutrons as its product. Neutrons produced this way induce radioactivity in the reactor structure, creating radioactive waste that must be disposed of.

Due to the problems of neutron radiation, the D-T reaction is not "perfectly green". Provided, the half-life of its radioactive waste for that process is overwhelmingly short, and it does not take much time before it becomes harmless (between a few decades to a few centuries). As this time to become harmless is around 8 half-lives, compared to even a single half-life of nuclear waste produced by nuclear fission, which is on the level of a few hundred million years, the difference is quite large.

The sun produces energy from a nuclear fusion reaction called the proton–proton chain reaction. Unlike the D-T reaction, neutron radiation is not produced. For this reason, it could be called the "holy grail of green energy". While the reaction does produce gamma radiation, this is converted into heat and less energetic X-rays, UV rays, light and so on within the sun. As of now, it's impossible to reproduce this on Earth.

In what way Yatagarasu performs nuclear fusion is unclear. In Touhou Hisoutensoku, in Utsuho Reiuji's winning expressions, it seems that she uses hydrogen as fuel to make nuclear fusion occur. Both of the aforementioned reactions use hydrogen (the D-T reaction uses its isotopes).

For the proton-proton chain reaction, as the holy grail of energy, the scale of this reaction – like the sun – would be different on the order of several tens of digits.[Ref. Needed] On Earth, much less the size that Utsuho could handle by herself, if it was implemented, its output would remain a considerable problem.[clarification needed] If the D-T reaction was used, the problem of neutron radiation exists and would contaminate the surroundings. Furthermore, both reactions have a high activation energy (about a million degrees Celsius would be necessary). However, in Gensokyo, Yatagarasu could be using divine power to circumvent this barrier.

Due to the nature of Utsuho's ability, mishandling the reaction carries the risk of widespread radioactive contamination.

Since, according to the spell cards, a chain reaction fundamentally does not occur[Ref. Needed], it's not possible to collapse into an uncontrollable nuclear meltdown accident. The criticality/loss of control problems of the present-day nuclear reactors are all fission reactors (for instance, Godzilla)[clarification needed]. Interestingly, Utsuho's third arm has the "control rod and fuel rod" attached, features seen in fission reactors but not fusion reactors.

Furthermore, Utsuho uses a control rod and performs nuclear fusion, but how she uses it is not quite clear. It is commonly thought that she uses it like a weapon as a heat ray cannon or a beam rifle.

Parallel Evolution

In Curiosities of Lotus Asia Chapter 14, Rinnosuke Morichika mentions that the Kappa are often mistaken to be related to the Chinese river youkai/god known as a Kahaku. He tells Sakuya Izayoi that while they may have similar names (And presumably similar in many other ways to the point of being identical), they are two completely different creatures. He states that just because there's a youkai with a similar name in an country (It is assumed this means outside the Japanese archipelago) in the outside world, to think that they are the same creature is unreasonable.

This is known in science as parallel evolution. This may also be the case of why Oni and Vampires share portions of their name and have identical weaknesses, while they are clearly two different species of youkai. Because modern science is fairly new, similar supernatural creatures may easily be grouped up as the same thing.

While the subjects used to explain this is far from modern science, this subject was only understood recently after the discovery of genetics.


DNA is the genetic instructions used in the development and functioning of all known living organisms (with the exception of RNA viruses).

It is first mentioned by Aya Shameimaru in Double Spoiler during Koishi Komeiji's spell card as some kind of swirly thing that controls humans. Not entirely wrong but far from right. Judging by Hatate Himekaidou's comments and Aya's knowledge of it, DNA is not well understood in Gensokyo (Former Hell may be far more advanced as far as modern science in supernatural worlds go).

Primate Spirit Garden

Keiki Haniyasushin turns the Primate Spirit Garden into a high-tech fortress during the events of Wily Beast and Weakest Creature