Shoko Arima is Setsuna's classmate and constant bully as well as Hina's master after a spell binding contract goes wrong.
Arima has a long hair which extends all the way to her back. She is tall and has a curvacious body almost resembling a perfect hourglass figure. She is seen mostly wearing her school uniform even while on a date.
Introduced as the constant bully of Setsuna, Arima is the sole heiress of the Arima Group in which she takes advantage of her status to gain the utmost respect from her classmates up to the point in which Kana describes as "the one who holds weight in the class". She calls Setsuna her servant and orders him arround without hesitation. This is also the same for Hina (who became her slave after a spell mishap) in which she constantly gives multiple orders at once. She lives at odds from her parents and lives alone in an apartment. She shows signs of laziness and gluttony while in her apartment in which Hina remarks never gaining weight no matter how many times she eats. She easily loses her temper even for simple insults from Kana or when Hina forgets to call her "master".
But despite her nature, she rarely shows signs of being spoiled to other people and her constant bullying of Setsuna is only to mask her feelings for him. It is shown that she deeply cares for Setsuna as she once said half-asleep that "she won't let the Kana and Rena take hime away because he was her servant".
Arima is an average teenage human girl and lacks skills of the Oni Princesses yet is physically strong and capable to defend herself. She also has a magnificent singing voice.