Kinda ate with this one… see i wrote Yichen to be obsessed with Yuanzhou even after 10 years of marriage because he sees him as his equal and a person of his own ambitions. He’s in love with him to being obsessed with anything he does but he respects and gives the other space to DO what he does.
Li lun is much different, canonically and lowkey how I wrote him. His obsession comes from love but he saw Yuanzhou as something to possess and hold, he saw them as equals but eventually it somewhat shifted with jealousy. He was jealous to a degree that YZ was so well liked and loved by others (the human realm) and the idea of him being the Baize Goddess only heightened his worries because he didn’t want him to be seen around others, he didn’t think the world was worthy of being “equal with Yuanzhou like he was” or “being graced by his presence alone”
It grew to an obsession that he just wanted him to himself forever, that’s why he really messed up everything and did all he could to tie Yuanzhou to himself forever if they both shared the Baize Token. They would be “equal” in this way, no one be separated or better than the other to the public eye.
(I’m talking about my fanfic btw, this isn’t the same logic applied to the show but there is some truth in it still- I always thought LL was really possessive over Yuanzhou and jealous that he was so well liked by the human realm (somewhat), until they turned their backs on him (cause of the red moon) and LL got to the point the finger and say “SEE! The world hates US, you can’t trust humans, you should only trust ME, the demon you’ve been with since birth! Stay with me only because I am your other half”)
Same type of mindset ya know, very sad but he breaks free from that in the end woo!