Every soulmate AU I have for them involves Kotetsu having two soulmarks/two soulmates, because I can't fathom a world where he and Tomoe weren't soulmates, too.

And yeah, you're probably right about me underestimating people. Which...is not something I needed to know because I will literally write a dozen soulmate AUs for Barnaby and Kotetsu if I have the time. >.>