ストレンジマスカレエドハロウィン (Strange Masquerade Halloween)

Background
Why don't we start the party? Strange Masquerade Halloween is a halloween song uploaded by Machigerita.

A couple of people get an invitation to a Halloween party and are instructed to wear masks. They find the house who sent them the invitation and he tells them to enjoy themselves while maids bring in food. As time passes on they become more crazed and loose themselves, they eat, dance and have sex. However, a girl realizes she can't remove her mask and soon all party guests are transformed into monsters to match their masks. The host laughs, stating that "the pleasure will continue forever".