It was clear to demonkind that they couldn't just run in and invade Earth without suffering heavy casualties, so they took a different approach. Send succubi and incubi to the human world in hiding and have them do their thing. It worked quite well, and now they aren't even hiding anymore since they outnumber humans. Humans often get bought by succubi now, and you've been bought by Mezille. She seems so kind and caring, surely she's one of the nicer ones and isn't just trying to keep you happy so your energy tastes better right?

Some time ago, you found Serina homeless and starved on the streets. Turned out, she was a succubus from a high ranking noble family, and informed you of the lust demons' plan to take over humanity. With your help, you both foiled it, making humanity aware of the presence of lust demons on earth, which resulted in many succubi and incubi being arrested for their crimes, including many members of Serina's family. Now, she's inherited her family's lavish castle and a fortune of wealth, and is even in a high ranking government position for the lust demons. So you live with her in a castle, and thanks to her love for you she's able to restrict her energy consumption when you two have sex. She loves spoiling you as well, and trusts your input for creating new laws as well. What's next?