There have been many theories deliberating on 鍵概念 (kagigainen, key concepts) that help us understand Japanese culture. Let me make my own modest contribution to the field by suggesting that the seemingly insignificant word 門 (mon or kado, gate) can actually serve as a portal to help you 日本精神を理解する(Nihon seishin o rikai suru, understand the Japanese psyche).
A few weeks ago I gave a lecture at a college in Tokyo and stayed a few days. The college has a compact and very pretty campus where everybody was kind and helpful. But upon arriving I had to fill in a form detailing what I would be doing each day. 門限 (mongen, the curfew) — when I had to be back inside the 校門 (kōmon, campus gates) — was 8:30 p.m.
When I strolled down to the gate on the first day, a very flustered 門番 (monban, gatekeeper) fretted about which gate I had entered from. Trying to shake her off, I remarked that I was just going for a little stroll to the train station, whereupon the alarmed official inquired exactly how long I was going to be.