Techniques from tanto tori.

Knife held normally (blade down): tenshin or tenkan.

Knife held blade out: irimi into gokyo or tenshin and guide uke's arm away with your (original) rear hand.

Think about how you would do techniques against tanto. Run thru your inventory of techniques and discover what will work and what doesn't work. This is how you learn.

New people think that uke is taking falls. Later on you realize what the really important questions are.