Yamato Nadeshiko Shichi Henge

We're in the Middle of Studying Right Now (1x11)

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Sunako needs to be tutored in math or else the rent will go up. Also, the girls are in an uproar as Kyouhei dresses up as a nerd and studies hard to teach Sunako not to run away. In the end Sunako still failed the exam because she put the answers in the wrong number.