Ascot is a young Palu with a rare gift—he can summon monsters that he genuinely considers friends. They're pretty grotesque by anyone's standards, but they mean well. Unfortunately, nobody else sees it that way. The villagers wanted nothing to do with him or his creepy companions, so when Zagato showed up offering shelter and purpose, Ascot jumped at it, agreeing to fight under him in exchange.
His time with Zagato didn't end well. In the anime, his monsters wreck Presea's house, which directly leads to her death. When the Knights finally call him out on it, Umi doesn't hold back—she slaps him for using his friends like disposable weapons and hurting them. It's a wake-up call that actually works. He ditches Zagato and has a genuine change of heart.
By the second series, things have shifted pretty dramatically. Ascot willed himself into adulthood purely because of his feelings for Umi. He's still summoning monsters, but he's learned actual spells from Clef now, so he can fight without putting his friends on the front lines. He manages to confess to Umi before she heads off to fight Tarta, but her response isn't what he hoped for—she cares about him, sure, but no more romantically than anyone else in Cephiro. It stings, but he doesn't give up trying to win her over.
Content compiled by AnimeList.moe from publicly available sources.