Aldebaran

Al is Priscilla's knight. Initially introduced as Priscilla's constantly abused "knight", it is soon revealed that there might be more to him,

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following the revelation that, like Subaru, he was summoned to this world from Japan roughly 18 years ago

. Although very skilled at fighting due to the time spent in Vollachia, Aldebaran does not like to make enemies, as he considers that taking care of them when a problem occurs requires a lot of work, but Priscilla doesn't seem to care about this.

Al has a frivolous and goofy personality, and

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having spent more than ten years in a different world, he was easily able to get along with Subaru

. Despite being Priscilla's knight, he doesn't really recognize himself as one, seeing himself as her caretaker, while Priscilla herself sees him as a handyman and a jester to entertain her. He has no qualms about their relationship. He also brags that the only way he can fight is by outwitting people and catching them by surprise.

Despite his easygoing attitude, Al is deeply affected by having a form of amnesia. Until he met Subaru he sometimes had episodes where he would think of himself as losing the plot

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due to the memories he had from Earth

. It's unknown how Al's amnesia came to be.