Kaito(u) + Ran?
I ship them friends, or at least with a deep comraderie! ^_^ There are three ways this can go.
1. Comfort sex partners leading to a deep and heavy friendship that I would read the hell out of, omg, so much being lonely together and commiserating without ever actually falling in love. Wibble. :D Suddenly I need this in my life.
2. Sharing Shin’ichi. (if KaiShin is applicable) (may or may not be sexual with each other)
3. Bonding over “you will never believe what that idiot detective did THIS time, arrgh!”