Culture
The act of expressing gratitude differs slightly from the need of providing gifts. Even if you bring a gift for your Japanese host, it is polite to send a handwritten thank-you card after your trip; it would be greatly appreciated.
You should be prepared to receive several photographs of you and your hosts together as Japanese guests are known to regularly exchange photographs taken with their hosts. An online communication can be sufficient, depending on their age and the type of relationship you have with them (personal or business).
In Japanese culture, the old are treated with considerable respect, and they are accustomed to the perks that go along with it. A bold obaa-san with her eye on a seat may surprise others waiting to board a train by shoving them aside. Be aware that many trains have designated "silver seats" for the elderly and those with disabilities.