Here is her character description, via the game’s official website:
Jack-O’ is an artificial life-form created by Asuka R. Kreutz to prevent the revival of Justice, the herald of destruction.
As Justice was created using Aria, Sol’s love interest in the past, as a base, Jack-O’ managed to prevent Justice’s awakening by fusing with Aria’s soul within Justice. It was at this time Aria’s soul was fully restored within Jack-O’.
However, Aria’s consciousness has yet to fully manifest, leaving Jack-O’ in an unstable state where her personality remains unchanged.
Although she tries her best to be cool and collected in her demeanor, she tends to act child-like when her emotion gets the best of her. For that reason, she wears a special mask to keep her composure during battle.
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