Ascot is a Palu, a young child with the unusual ability to summon monsters, whom he considers to be his friends. Although hideous, they have no ill will, but villagers still fear them. Thus, Ascot was driven away until Zagato offered to give him and his friends a home in exchange for serving under him. In the anime, he destroys Presea's house with his monsters, and essentially causes her death; later, he confronts the Knights again (their first encounter in the manga), but Umi slaps him for using his friends and causing them pain. This causes a change of heart in Ascot, and he then forsakes Zagato. In the second series, he has used the power of his own will to make himself into an adult because of his love for Umi. Also, he still summons monsters but has learned other spells from Clef to avoid using his friends as living weapons.
In the anime he is able to tell Umi his feelings before she leaves to fight Tarta. Umi replies that she loves him as well, but just as much as everyone else in Cephiro, and that she didn't have any romantic feelings for him. This saddens Ascot a bit, but he still tries to win her heart later on.
(Source: Wikipedia)