I want to think that Ienaga did nibble on a bit. Sugimoto is joking because her sudden desire to rescue Asirpa is the same as his thus it made him think that maybe her assimilating a part of his brain passed onto her his deep affection for the lovable Ainu daughter.
I may be mistaken, but I believe perhaps it is foreshadowing Ienaga’s sacrifice to save Inkarmat and Tanigaki’s child, stemming from unbelievable courage you wouldn’t have expected from her but from Sugimoto alright.
Man, I really love how yesterdays enemies could be todays allies. It's just so cool to be able to see so many different characters interact with Sugimoto as both enemies and allies.