Hattori goes on a mission to prove that Mr Mitsuba is a hero.
Mr Mitsuba returns home one night to find his family seated at the dinner table. He asks Mrs Mitsuba if the light bulbs have been replaced and if the mice have been chased away, and Mrs Mitsuba says that Hattori did those jobs. Kenichi and Shinzo praise Hattori with utmost reverence. Hattori grins modestly, but then a jealous Mr Mitsuba storms off to his bedroom.
Next morning, Mr Mitsuba hears Kenichi and Mrs Mitsuba saying that they wished Mr Mitsuba weren't around. Horrified, he goes out into the garden to calm down. The scenes then switch to the master bedroom, where Kenichi is looking at a photo of a newly married couple that Mrs Mitsuba took. He says that she didn't need to include Mr Mitsuba in the photo, but Shinzo deduces that she included him in the picture because she loves him, and Mrs Mitsuba blushes.
In the garden, Mrs Mitsuba asks Hattori to clean the gutters before the storm hits. Hattori, seeing his chance, goes forward, but Mr Mitsuba proudly announces that he'll do it himself. Nevertheless, Hattori tries to do it, but deliberately trips over a pipe and falls down. He then leaves Mr Mitsuba to it, and the family patriarch does it really well.
After the rains hit the sky and fall to the ground, Kenichi asks Mr Mitsuba to build his model submarine. He makes a bit of a mess first, but with Hattori's help, he builds it. The family praises him, but then he remembers what they said about him earlier, and is hurt.
Later on, the family explains the misunderstanding to their patriarch, and he forgives them. Just then, a thunderbolt strikes, startling everyone. Everyone, that is - except Mr Mitsuba. The family then spend the rest of the day in harmony.