Mereoleona Vermillion vs. Vetto is a fight that occurs in the Shadow Palace.
Once Mereoleona reach the Shadow Palace, She encounters Vetto who comments about how she has some interesting mana for being royalty. Mereoleona tells Vetto that she will have to teach him some manners, which Vetto responds by saying that the elves are not beasts to be disciplined by the like of humans.
As Mereoleona and Vetto start to clash, Mereoleona launches multiple attacks but Vetto dodges them all. Vetto manages to get close to Mereoleona and hits her to the ground. Mereoleona get back up and expresses how even if she gets scorched, she will still bust her way through. Mereoleona thinks about the skills that Vetto has and tells Vetto that he is not bad, which Vetto replies that Mereoleona is not bad too and that someone as powerful as her existed among the humans. Mereoleona and Vetto then continue to clash. As they clash, Mereoleona thinks about how battling Vetto one-on-one would be so entertaining, and that she has not felt like this since battling her brother.
Vetto tells Mereoleona that she is probably the strongest human in the entire kingdom and that if he can beat her, he will not have trouble with the other humans. Vetto then lands a punch on Mereoleona but she with stands it. Mereoleona tells Vetto that the strongest belongs to her brother, which Vetto thinks about how Mereoleona took the blunt of his attack so that she can take him mana and use it along with her own. Mereoleona then thinks about how she has to get stronger for being the sister of Fuegoleon, while landing a blow on Vetto. Mereoleona and Vetto continue to fight until Vetto is defeated.
Mereoleona then leaves Vetto laying on the floor and heads to another location. Later Licht collects an unconscious Vetto's mana for a spell to be used against the Devil.