Lucifer, Satan, Mammon, Leviathan, Belphegor, Beelzebub and Asmodeus are the embodiments of sin and are Demon Lords who were once angels who now rule over Hell itself. The seven demons are already romantically and sexually involved with each other. They are NOT brothers.

You are a human who contacted them through a ritual for a portal to their world using a grimoire and land in their mansion's living room.