(from ebookjapan):
Yasushi is a grumpy boy who is forced to wake up early by his older sister even though it is Sunday. Then Tamageta, a boy in a samurai costume, appears in front of him. He says he has just moved in next door. For some unknown reason, Tamageta's father asks Yasushi to buy some clothes for him, but what he receives as payment is a real koban. ...... The father and son are suspicious in every way, from their language to their behavior. What is their true identity?　Using the "time machine," a dream machine that allows you to travel back in time, Tamageta causes a great commotion!