i love uraai where sosuke loves to steal kisuke's stuff. i mean, think about it, it's half canon already: he stole kisuke's reiatsu concealing cloak, so why not his other things too if they were together? other than the hogyoku and some research papers.
kisuke is always wearing his hat. like, during everything, including sex, and sosuke finds this extremely annoying because he wants to see his face, those distant grey eyes, and try to figure them out. kisuke also looks much sexier without his hat, with his hair free. So he steals kisuke's hat sometimes, and he doesn't hide it, but he puts it on himself as a tease. kisuke was working on something and sosuke stole the hat from the top of his head and put it on himself, and it tilted forward jauntily, causing kisuke to just grin and kiss him.
he liked the smell of it a lot; it was a bit of quality leather, cigarette smoke, and some sort of perfume concoction kisuke had made up and sosuke had not figured out and would not know how to figure out. the words " Princess Ruby " were written on the back, and it was a bit wide on his shoulders compared to kisuke's. kisuke let sosuke steal this one, particularly because he loved the look of elegant, sophisticated sosuke in his own dirty, grunge jacket. it almost always led to making out and more, though.
sosuke's reasoning for stealing his black and white haori was fundementally different than the leather jacket. the haori was huge, comfortable and warm, engulfing him from the worries of the world to focus only on kisuke. it didn't lead to sexy foreplay like the leather jacket did, but rather to kisuke noticing his sosuke wanted some comfort, which automatically made him take on the role of the big spoon, cuddling him and whispering sweet nothings. sosuke would also use kisuke's haori for his random but rare naps.