trolley - small one.

If you think you'll need to haul a sizeable bag around, save your back and send it by takkyubin - http://www.japan-guide.com/e/e2278.html

Keep a couple of night's worth of clothing with you (in that small trolley) and imagine yourself as a rich person in the golden age of porters.

It's one of the great perks of travelling around Japan. Indulge!