Still don't think it's Yukiko.... Yukiko never stopped acting, she's always playing it up for an audience (family, friends, perfect strangers).

Fit in all the characters is going to crimp the screen time for our lovely detective boys so I hope it is a scroll by or a flashby in a bad dream of Conan's.

Oh no, Heiji cross-dressing!! Only if it's in a doujinshi in order to seduce Shinichi please. ^.^