I cannot for the life of me think of a better way to explain this, so Diagram Time.
*“this” being sexual desire
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I cannot for the life of me think of a better way to explain this, so Diagram Time.
*“this” being sexual desire

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Can you write in detail about SJ's character? (His wants vs what he needs, his flaws, how he perceives people and how he perceives himself etc.)
I think an entire summation of SJ’s character is a bit much for one ask, but I can answer the first question!
I’ve been dwelling on this for a while and haven’t been able to put my thoughts into words, so I have made this handy diagram instead:
Basically, I think his absolutely core (but unacknowledged) desire is to feel safe, and from that stems the desire for control that defines his character. The conflict between SJ’s needs and wants often emerged when SJ misinterprets or disdains the core desires, and instead ends up chasing after this band-aid solutions.
As for his needs, ignoring the bottom rung of Maslov’s heirarchy of needs, the first and most obvious answer is that SJ needs some kind of treatment for or way to manage his mental health, specifically his cPTSD. In canon, SJ is stuck in survival mode, and no positive change can be built on top of such a shaky foundation. In relation to that and the aforementioned desires, he needs to feel safe, but the path to achieve that is its own complicated question (and is that not what qijiu fic is for 😂). I haven’t thought as much about his needs beyond that, but I think SJ does best when he has someone he trusts and feels safe with (I obviously have a biased suggestion for who that should be, I think there’s options), and it can’t hurt to give him something to do that he has complete power over but that which doesn’t too heavily effect other people (a hobby where he can go complete dictatorial godking. BDSM would also work).
My friend @/levia-san has said that SJ would be happiest as a big fish in a small pond, and while I still think there’s the issue of his ambitions, in terms of what would satisfy his psychological needs that pretty much covers it.