Doting Aunt

"Aunt Hanabi, any time I say 'do for your nephew' after I ask you to do something, you'll find yourself becoming incredibly doting and loving of me, and you'll want to do whatever it was that I asked, because a good Aunt spoils her nephew" he said with a grin.

This way, he could basically make her do anything he wanted. Even if it was weird, seeing her naked like this was turning him on. He figured if he did end up wanting to push her further, this trigger would allow that.