I've heard it theorized as the difference between Reimu as seen through Kasen's eyes and Reimu as seen through Kosuzu's eyes.
Was just about to say this myself. Kasen is... Kasen, so she sees Reimu and Marisa as silly children. She admits herself that she underestimates them, though, and I personally think they already know she's an Oni, but Kasen, being arrogant as she is, likely thinks she can fool the two best Youkai hunters in the world, let alone Reimu's perfect instincts.
Kosuzu is a young village human with very little experience, so she sees the two as cool young ladies, and she sees Reimu in particular as a cold-blooded badass.
Further evidence for this theory can be found in how condescending the character titles are in WAHH, at least until Kasen learns to respect people. Each of the manga is written from its main character's perspective. This is why so many different interpretations of the same character can all be valid. We can't see Gensokyo as it really is, we can only see someone else's version of the story. Unreliable narrators being the law are what make Touhou as fun as it is.
Was just about to say this myself. Kasen is... Kasen, so she sees Reimu and Marisa as silly children. She admits herself that she underestimates them, though, and I personally think they already know she's an Oni, but Kasen, being arrogant as she is, likely thinks she can fool the two best Youkai hunters in the world, let alone Reimu's perfect instincts.
Kosuzu is a young village human with very little experience, so she sees the two as cool young ladies, and she sees Reimu in particular as a cold-blooded badass.
Further evidence for this theory can be found in how condescending the character titles are in WAHH, at least until Kasen learns to respect people. Each of the manga is written from its main character's perspective. This is why so many different interpretations of the same character can all be valid. We can't see Gensokyo as it really is, we can only see someone else's version of the story. Unreliable narrators being the law are what make Touhou as fun as it is.
But the manga shows events that Kasen and Kosuzu don't know about, like when they aren't present or the latter is unconscious, so they can't be the narrators or have the story be shown in their perspective. Plus ZUN himself said in SCoOW that his works have omniscent narrators (except Aya, Marisa and Akyuu's books, but those aren't really stories and more like encyclopedias) and that we'll never know how Reimu really is. Reimu changes drastically between games too so this isn't exclusive to the manga.
But the manga shows events that Kasen and Kosuzu don't know about, like when they aren't present or the latter is unconscious, so they can't be the narrators or have the story be shown in their perspective. Plus ZUN himself said in SCoOW that his works have omniscent narrators (except Aya, Marisa and Akyuu's books, but those aren't really stories and more like encyclopedias) and that we'll never know how Reimu really is. Reimu changes drastically between games too so this isn't exclusive to the manga.
They do have a consistence viewpoint though. In FS, it's the viewpoint of the (mostly) normal villager, seen when the cast is on duty, the side that look at all the incident happen in gensokyo from the outsider look. While in WAHH, it's more of an insider look, seen when the cast is off duty, the side that look inside the blackbox that is the incident. And Reimu, being Reimu, end up looking different from different point of view: Match with no one, and clash with no one.
I've never made anything from Reimu's point of view. The games are written in third person omniscient, so only she knows what she's really like. I don't know very well either. We have no idea what's going on in Reimu's head, so she changes depending on whose perspective we see her from. The Reimu that youkai see, the Reimu that fairies see, and the Reimu that humans see are all different. That's probably because she's in a bit of a different position from the protagonists of other works. Also, no matter what work she's in she never grows up at all. She might actually be pretty similar to a final boss. ...In "Urban Legend in Limbo" she finally overcomes that final boss side of herself and shows her true character (lol).
To me, it feels as if she has the pure heart of a child, the contradictory wisdom of an adolescent, and the mature intellect of an adult. As such her personality differs depending on the situation she's in. It makes for a strangely fitting and interesting protagonist, I suppose.
FS shows more Reimu working, WaHH more slacking off, but WaHH Reimu still does her best at work and FS Reimu is still silly in those festivals. If anything, FS Reimu is more experienced, she gives off a capable and serious vibe. WaHH Reimu need plenty of help so even if she is sincere it looks like she is playing.
To me, it feels as if she has the pure heart of a child, the contradictory wisdom of an adolescent, and the mature intellect of an adult.
^ This She is a person you can't love or hate, as she changes from time to time.
'ey, you an Oni?
I think you might be.SCARY!What dreadful bloodlust...Please take good care of me, you two!Dude, she's adorable...Is she a goddess?I wonder what that machine does...