"He'll be Neiro's" uh fuck you no he won't. He's a living human being with his own free will and legal rights. If you want him to go with you in any sort of permanent fashion, that'll be entirely up to him, and any attempt to just pick him up and carry him off by force will very swiftly land you on the wrong side of the law. This is the world of manga, so this current instance of literally picking him up and (presumably, since we have to wait 'til next chapter to find out for sure) carrying him off will be hand-waved away, but that's because it's not permanent. If she were to somehow win the challenge (which she won't bc MC privilege), she'll have no way to enforce her price.