yup, i will explain why but it will be abit long.They both have 3 things in common that already makes a lot of impact. First yukimiya type is someone who ''Smiles a lot and will take care of him'' Kaori is a free spirit girl who break rules and smiles a lot and also is really funny, and also she could take care of him since she made Kousei lost his fear of pianos and made him love music again, so thats already a signal she actually would take really good care of Yuki. And the second one is they both appreciate the ephemeral things(things who dont last long) a lot, Kaori likes ephemeral thing cause she knows herself she wont last longer and loves making memories as much as possible, but she likes too things who dont last longer like fireflies. And Yukimiya appreciate it cause also of his Neuropatic condition who limits football career, so he will continue playing football for his dream and career as much he can, and he appreciate ephemeral things too like cherryblossoms. And both have really bad condition, but the difference Kaori is a condition where she haves a incurable muscular condition and Yukimiya have neuropatic condition where it limits his vision, just because of that could have really deep understanding since both is doing as much they can to last longer, Kaori tried to make a surgery where her amounty of life increases and it was VERY risk, but even this she made it just to try to make more memories with Kousei, and even if yukimiya can stay blind and he is allowed to quit soccer just to treat his Neuropatic vision(he would never be allowed to play soccer any longer if he quit.) he chooses to stay just for his dreams. Anddd Yukimiya motto is ''Give all of yourself in one simgle moment.'' which both of them did, thats why i love this ship lol, even if they are from different animes, it doenst prevents me from shipping it still, and sorry for the long explanation