YMDD-405 - Privacy invasion observation and depiction of inappropriate acts

It started with a simple whim. I secretly filmed my niece 'Kana' and her friend 'Konatsu' who often came to play, and... They were engaged in lesbian acts, masturbation, and immoral infidelity with their boyfriends! Moreover, I was caught filming them secretly and unexpectedly found myself in a 3-person sexual abuse situation! The entire process until I was thoroughly understood by the precocious sexual skills of the underage girls.