Post/Stained pants of the son's wife (28 years old)

The author is in his 60s living with his son and wife. He said he was tired of enjoying his son's used pants before washing (28 years old) by making effective use of the situation that he stayed at home all day on weekdays. If you think about it, the current 60s are still well unlike the old-fashioned image. Perhaps this is what's going on in this house.