Soulmate (platonic in this specific scenario but you can read it as romantic) JiuYuan that share habits and quirks even through different worlds.
Like Shen Qingqiu having a nightmare of the past (which is why he tries not to sleep often) and there’s like this invisible being guiding him. It leads him from his abode down to the kitchens—still open to a few of the late night stragglers that can’t find sleep. When there the staff are surprised to see Shen Qingqiu there, especially since he mainly practices inedia. Shen Qingqiu isn’t quite sure what he’s doing there either, but he finds that the invisible force wills him to order something—anything, so he does.
Shen Qingqiu orders some soup, it’s the quickest thing to put together since he’s aware that the kitchen always has some available. Then, he drinks it right there, standing in front of the kitchen workers as he downs it in a few gulps. A sense of satisfaction wells up in him and there’s this subtle comfort there. It’s not quite enough to scratch at the itch now plaguing him but it’s a start.
It doesn’t become a recurring habit until it happens while he’s down the mountain. While taking his students for a trip down the mountain for a mission or whatever, something leaves him stressed (maybe LQG, maybe an upcoming visit to MQF, maybe memories of YQY emerging, idk) and the compelling force is guiding him to the market. So he follows (the force has never done him harm) and it’s there, after buying armfuls of sweets and gorging himself, that Shen Qingqiu learns the ways of stress eating. (It’s why he keeps snacks on him at all times now)
On Shen Yuan’s side things happen when his illness flares up, like he’s dealing with the normal pains when an invisible force seems to whisper in his ears, telling him to put his pain in a tangible form. So Shen Yuan takes up painting. He doesn’t paint peaceful landscapes, it’s actually mostly just random monsters he thinks up to best match his pain for the day—but it’s a habit that’s rather quickly picked up.
And then it just goes back and forth, it’d be like so funny if the reason why SY is a keyboard warrior is because SQQ takes pleasure in sending scathing, aggressive letters to those that irritate him (and he also sends rude letters on behalf of SQH, much to SQH’s surprise. SQQ doesn’t like people who fuck with his budget and has no problem airing it out in place of SQH, that coward.) or vice-versa.
SY’s love for novels being what lead to SQQ become a scholar is so funny :3
SQQ disliking men giving SY a (watered down) similar dislike and potentially even self image issues
SQQ’s wrecked meridians being why SY is sickly in the other world (sickly SY headcanon)
SY’s attention to details (negatively, esp when it comes to stories) transferring over to SQQ and how nitpicky he can be
