The key to it all is the observation that Ikebukuro Station is a terminal of the Marunouchi Line, so all trains always start empty on that platform. This double-queueing ritual gives passengers a tradeoff that would not be available in most other cases: speed vs comfort.

If you're in a hurry, you can directly join the senpatsu crowd and be (almost) guaranteed a spot on the very next train, but forget about sitting down—be ready to stand squeezed like a sardine. If, on the other hand, you have plenty of time, you may decide to get in the shorter kouhatsu queue—which will become the front of the senpatsu once the next train leaves—and you'll be (almost) guaranteed a comfy seat in your long commute.

For an Italian like me, this whole process is nothing short of a miracle. I grew up in a city where metro train boarding during rush hour feels like a prelude to the apocalypse.

Many Italians can come up with the idea of waiting for passengers to get off before boarding themselves, but most crowds there lack the restraint to apply it with any kind of regularity. When it comes to the strategy of directly aiming for the next next train, though, I wonder if it has ever even occurred to anyone south of the Alps.

[...]

Live in Japan as a foreigner for a while, and you'll see miracles of this kind everywhere. No one steals, even when people leave their purses and smartphones and wallets unattended in plain sight for half an hour at a time; no one litters; no one disturbs fellow train passengers by talking loudly or making phone calls; and people are extremely polite and go out of their way to help you if you ask. In Japan, you will only witness restraint and patience, even in the face of rudeness and selfishness from strangers. What kind of DNA compels them to behave in such a coordinated and collectively useful manner?

Of course, I know that there is nothing innate in the miraculous "Japanese Way" because expats living here quickly adapt to the same behaviors.

It's not just the ethnic Japanese that correctly follow the senpatsu/kouhatsu queueing system, for instance. All the long-time expats I know in Japan are—at least in public—just as polite, restrained, and rule-following as the average Japanese, regardless of their nationality. I wrote that no one steals unattended wallets in Japan, not that no native Japanese steals.

[...]

The real core value of Japanese culture (or one of them) is something like "never stand out or make a fuss". Nowhere in that principle is a strict requirement to follow the rules. In fact, it's perfectly fine, in Japan, to break the rules as long as that's what everyone does and expects you to do. In terms of framings, the Japanese culture has acquired—by arbitrary and unimportant means—a definition of the concept of (or a "black box" for) "standing out" that differs from its equivalent in many other cultures: instead of being generally neutral, it is seen as intrinsically unpleasant and embarrassing.

[...]

The Italian culture has the concept of simpatia that translates awkwardly to English as "being a mix of likeable and/or charming and fun to be around" and doesn't even exist in Japan. I do believe that having this compact and convenient idea of simpatia makes Italians more conscious of the importance of being simpatico and seek that property in others. It drives their behavior in more or less explicit ways.

[...]

Each culture is made of shared framings—ontologies of things that are taken to exist and play a role in mental models—that arose in those same arbitrary but self-reinforcing ways. Anthropologist Joseph Henrich, in The Secret of Our Success, brings up several studies demonstrating the cultural differences in framings.