Custom #4: Bath time!
One thing I've found quite interesting in Japan is bath time. In Japan, most people shower outside of the tub, and then hop into the tub to relax afterwards. Everyone in the household shares the same bath water. You're supposed to add a bit more water when you get out of the tub, to refill it and warm it back up again for the next person.
In North America, you either shower or take a bath but usually not both. Also, you shower inside the bath tub, or in a separate shower room/stall. I've never really heard of anyone sharing bath water with other members of their family, except for small children. Maybe it happens, but it's just not that common.
I've noticed that most Japanese take a bath before bed time, and while this is also common in North America, many more North Americans choose to just shower in the morning instead. This morning shower wakes them up so that they feel more ready to begin the day fresh out of the shower.