Ippon Seoi Nage - into:
Ko Uchi Gari

Ippon-seoi-nage is usually defended by resisting the initial attack by moving backwards, or entering jigotai. This makes it ideal to be continued into Ko-uchi-gari.

The above video, arguably, demonstrates kata-te-ashi-ko-uchi-gari, as the tori's arm falls to the leg of the uke. This could obviously be progresses to ko-uchi-gake-mata-make-komi.