How strictly is the curfew enforced?
In both dorm and homestay, the curfew is very strictly enforced. Dorms have curfews, and homestay families may impose a curfew. Living in Japan means abiding by the rules around you: you need to follow them. Be prepared for less freedom on this issue than you enjoy in the U.S. Japan is simply more strict about having its university students home at night.
Most of the time, if you let the dorm manager or your host family know of an exception ahead of time, they will allow it. However, it’s polite and respectful that you ask, if you know you will be late.
You may have more freedom in the dorms since most curfews are 12 pm or even 1 am on weekends. But this depends on the dorm. Usually, host families want students to return home for dinner (often around 7 pm) unless you have made special arrangements with them ahead of time.