Touhou Headcannons

[Kirisame Cola]

What are your favorite Touhou headcanons? I'll go first!

• Tenshi and Youmu often spar with their swords to keep their skills sharp
• Alice does a lot more than just make her porcelain dolls, she also made every bit of furniture in her house and still occasionally makes furniture for those close to her
• Sumireko has those incense makers in her room and she really likes the smell of vanilla incense
• Yukari's room in her house is filled with tons of shiny/glowing material things such as lava lamps and the such
• Mima, Yukari, and Shinki get together in Makai every now and then and talk.
• Marisa has Mimi-Chan under her bed and will use her again if her broom is ever to break

[OkuuFallout]

I'm not really the type of person to have headcanons, but I guess there are some.

• One of Yukari's favorite pastimes is to bully Tenshi
• The incredibly common "Alice has a crush on Marisa", but also if Alice asked her out, Marisa would just casually accept, not really thinking about it
• Marisa's not-very-well-known shop has two regular "customers": Alice, for obvious reasons, and Patchouli, for less obvious but still obvious anyway (she wants them books back), which is the only time she ever leaves the mansion
• Sanae has a crush on Reimu

[Fellow]

 I have a few headcanons, many of which are embarrassing but I'll shoot.

• Marisa has some sort of deal going on with Meiling to allow for her safe passage into the Scarlet Devil Mansion. Most likely food related.
• After the events of Touhou 18 Reimu stashed some of the cards to sell for her own profit
• Aya is always poking about the Hakurei Shrine because of her crush on Reimu rather than for the sake of the Bunbunmaru Newspaper
• Mystia is constantly on the run with her lamprey stand because of her involvement in Choujuu Gigaku with Kyouko(Byakuren is not so happy)
• Shou and Nazrin are secretly in a relationship without Byakuren's knowledge

[Danzig87]

Here are my personal Touhou headcanons.

• The characters are official members of the Gensokyo Danmaku Sisterhood (GDS) which consisted of founding members Reimu and Marisa and all the girls from PC98, Windows (EOSD to UM) and the spinoffs (IAMP, SWR, DS, HM, ULIL, AOCF).
• The spellcards the Windows Touhous use are named after artists and songs of the 70s, 80s and 90s.

[KharaPlz]

Here are my headcanons:

• Raiko is actually not a tsukumogami, but in fact ONE in disguise. Her actual nature is that of a "vessel" of an angelic / divine being. That being is nearly omnifarious (but not to the point of God-level) that it could assume whatever identity / species it wants for their vessel.
• Yumemi has a German mom who died some point before her 18th birthday. (hence making Yumemi in my HC a haafu)
• Raiko does not have a surname by default. She gained her current surname by being adopted. (This and the above HC about Raiko is a part of my larger collection of headcanons about Raiko and a bunch of OCs I made)

[Dreamy-Eyed Yuuritsu]

I like to think that the PC-98 characters are actually still around in the Windows era. One of my headcanons is that Ellen's Magic Shop is still there next to the Hakurei Shrine (after Ellen desperately begged Yukari to have her keep the shop there) and thus bothers Reimu on a daily basis along with Marisa. Next to no humans travel to the Hakurei Shrine though so Ellen mainly does business with the supernatural beings who come to mess around at the shrine (?).

Shingyoku still dwells at the Hakurei Shrine, which really annoys Reimu. They have a sort of a rivalry with Aunn as the protectors of the shrine.

Yumemi and Chiyuri were actually lecturers at the university where Renko and Maribel are studying at. It is mentioned in both the prologue for Touhou Yumejikuu and in the Magical Astronomy CD that gravity has been integrated into the main Unified Theory in the Outside World, so there could be some canonicity to it (?)

Rika and Rikako are close friends with each other, and live near the Youkai Mountain so that they can interact more with the kappas. 

A bit off-topic but Sariel and Shinki are definitely related in some way. If Shinki is the creator of Makai, then could it be possible that Sariel is an accidental byproduct related to Shinki brought to existence during the creation of Makai?

[LudicrousFPS]

• Seiran has an inferiority complex because of Ringo but secretly has a crush on her.
• Reisen is a really bad singer and artist, but surprisingly good at parkour.
• Raiko makes guest appearances in Choujuu Gigaku and they play death metal. Hecatia plays rhythm guitar but they have trouble finding a bassist.
• Because of above, Raiko, not Saki, is the one with unmatched leg strength due to playing blast beats so much.
• Kagerou carries Wakasagihime around whenever she needs to go anywhere on land.
• Sanangel is real (th19 made it sort of canon though)