Hoooly fuck. I would need more time to write something that is actually coherent as it's 2:20 AM here and I just binged all of the routes and possible combinations, but is there (SPOILERS)
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a reason, a canon reason (I know, it wasn't revealed) that you, as an author, feel like it made sense for personally, for why Seren placed the anchor inside Yi kai's study? I probably don't want to know this reason (it's a lie, I do want to know this, as the pre-Seren seems like a really calculating, pragmatic person with a denial as a coping mechanism and I love these types of characters. What could she gain by doing so?), but would simply know if there, indeed, was some real reason behind her actions. Sorry if this came out somehow jumbled, but after getting to Yi kai's ending where he returns to his homeland and Seren realizing that his improvement is really only temporary, I just had to ask!
... to be honest, I will most likely return here to ask about the same thing in about 2 years or so if I don't think of anything.