Remember what you must do when they undervalue you when they t hink your softness is your weakness

Referring to the art of war.

In this situation, they would treat your kindness like some sort of advantage for them.

In this particular case, it is best to play along and let them think that they could take advantage of you.

At the right moment, you should unleash your inner aggressiveness and fulfill all of your goals/objectives while they're letting their guards down.