Thanks for the chapter!
Yes the Demon Lord is reborn!!! Ahahahahaha! Power corrupts and absolute power corrupts absolutely so now Ain will become the new demon lord due to being corrupted by the Dullahan's magic stone. Or at least once he gets over the indigestion, gas and heartburn from eating an OP Supreme grade magic stone without working his way up the grades. Just can't go from lowest grade to almost highest grade in one swoop without the body protesting.
Anywho, wonder why stone said he returned? Also, in LN while Ain was still en route to castle Claune informed her grandfather the Archduke about being engaged to Ain. Then at the end of the party, after finding out Olivia divorced her husband, he reveals both to her and her father Olivia's true identity which in turn makes Ain a prince. Hence, instead of complaints and issues raised by other nobles about Ain not having enough rank to marry Claune, she's now the one who might not have enough rank to marry him. Although Ain likely doesn't care about that type of thing as long as she likes/loves him, and she was only concerned about the nobles making enough of a fuss to delay or hinder her marriage to Ain. In LN she was very taken with him and found him to be way better than any of the other nobles and their children in terms of personality, etiquette, and honesty. Also, getting a Star Jewel probably granted all her romantic hopes on being engaged to a reliable partner she can love rather than a political marriage with some narcissistic, entitled, complete jerk of a noble.