I don't like Boutarou. Might just be me but he feels too forced. Also can't trust these weird haircut/eyebrows/bearded motherfuckers. And, we already know we can't trust him.
Despite this being "different" we know Fuu-chan's disposition will still end up somewhat like a yandere or rather, she's the real "succubus" as she'll end up enticing Yukiko later when the triangle becomes a thing. She's the real final boss and she'll win.