SynopsisEditMrs Mitsuba is furious with her son for scoring zero in his maths exam, and says that he keeps failing, he is lazy and that he has put the family into disrepute. Despite Kenichi apologising to her, she cottons on ruthlessly and says that he will start his homework the instant he sets foot in his room and that there will be absolutely no mention of comics, computer games or television for him until he learns to improve or there'll be hell to pay.
Later on, he confides in Hattori for help, but Hattori dismisses him, saying that he deserves to suffer because he has made Mrs Mitsuba suffer. With no one else to turn to, he asks Shinzo for help, and Shinzo promises to do so, as does Shishimaru. Kenichi is overjoyed. They rummage in Hattori's box of scrolls, until they find the one with the spell to change personalities. Laden with the scroll, they troop downstairs - unaware that Hattori is spying on them. They cast the spell on Mrs Mitsuba and stop her from cleaning the house, sending her to have a little lie down. Hattori isn't pleased.
The gang use their time away from Mrs Mitsuba reading comics and eating snacks, but Mrs Mitsuba comes in and tells them off for hogging the biscuits, before taking them herself. Later on, as the lunchtime bell goes off, the gang come downstairs, only to find raw vegetables on the table. They reluctantly begin to eat as Mrs Mitsuba insists they do so.
A few minutes later, Mrs Mitsuba goes to the shop. Kenichi and the gang worry for her, but Mrs Mitsuba assures them that buying products that are ten or twenty Yen more expensive won't be the end. She asks the supermarket attendant to put whatever he can find into the trolley to get dinner.
Mrs Mitsuba puts aside her diet and tells Kenichi she'll think about it when she puts on a hundred kilograms. Worrying for her, they turn to Hattori for help. Hattori says that only the person who cast the spell can undo it, so he assigns Shinzo to solve the problem. Not knowing how to undo it, he does it again - but it only makes things worse. Just then, Mr Koike visits. He nearly jumps out of his skin when he sees her on the floor. When Mr Koike tells Mrs Mitsuba about Kenichi's poor marks, she replies that he's a wonderful boy and no-one ought to complain about him. To fix things, Shinzo casts the laidback spell on Mr Koike - and he goes crazy too! Thankfully, Hattori finds the counter-spell and has Shinzo undo the technique. Kenichi is fed up with being in hot water - but glad that the spell is finally over!