Americans might be surprised by the ease with which Japanese people sleep on trains. In fact, they sleep everywhere—from park benches to meetings (yes, meetings). They even have a name for it: inemuri (“sleeping while present”). Sleeping in public is so normal in Japanese culture that it is considered rude to wake a sleeping person.
Japanese sleep during the day because they work hard and long and often do not get enough sleep at night. They make up for this by sleeping at work. Workers who sleep at work are considered to be more dedicated to their work than themselves. They’re sleeping because they’ve worked themselves into exhaustion, essentially.