It's 5pm on a Friday and I'm standing in a coffee shop above Shibuya crossing - one of the most famous intersections in the world.
It's a place where every two minutes, more than a thousand of Tokyo's smartly dressed commuters and fashion-making teens gather at eight points, ready to cross - then rush straight for each other.
It looks like they must crash, this sea of people, but they swerve and swing around each other, like dancers pirouetting, and they all get to the other side safely.
It's awe-inspiring, so much so that at times it leads people - including myself - to say rather trite things about how it's the perfect symbol of Japanese society: the many individuals acting together for the greater good.
But the reason I'm here, isn't to gawp in amazement, it's in the hope that I'll see people crash.
I want businessmen ploughing into each other, their umbrellas flying off their arms, and immaculately uniformed schoolchildren tripping up grannies.
Why may I get to see this now, when I wouldn't have had the chance even a year ago? It's very simple - smartphones.
Smartphone use is booming in Japan. In 2012, only about a quarter of Japanese used them, most being perfectly happy with their everyday mobiles.
But people have now realised smartphones are just too useful to ignore, especially because they can be used to read newspapers and manga, the Japanese comics which have gone global, without straining your eyes.
More than half of all Japanese now own a smartphone and the proportion is rising fast.
But with that rise has grown another phenomenon - the smartphone walk.
It's that glacial pace people only adopt when they're staring at a phone screen - their head down, arms outstretched, looking like zombies trying to find human prey.
Researchers here have found people don't just walk more slowly when they're on smartphones, their field of vision is reduced to 5% of what it should be, and some are worrying what this means for Shibuya.
Recently the Japanese mobile giant NTT Docomo released a simulationof what would happen there if everyone crossing was doing the smartphone walk.
There would be more than 400 collisions every time, it said, and most likely just 36% of people would get across. Orderly Japanese society as we know it, would be at an end.
Surprisingly, the person who seems most annoyed about this phenomenon is an American.
Michael Cucek is a consultant who has lived here for more than 20 years. In his spare time, he writes a popular political blog called Shisakuthat has recently been littered with posts about what he calls "dumbwalking".
I met Michael this week in Sugamo, a part of Tokyo popular with pensioners who, understandably enough, all walk incredibly slowly.
He told me dumbwalking probably wouldn't be a long-term problem.
Japanese phone etiquette is in fact better than anywhere else in the world - hardly anyone speaks on their phones on trains, and teenagers wouldn't dare broadcast music out of one.
If things got truly bad at Shibuya, the police would just start patrolling the crossing shouting at people to look up. Until that does happen, though, he's going to carry on ranting.
But really, is the smartphone walk such an issue? There's only one way to find out. So I leave the coffee shop, head down to the crossing and start typing an email, promising myself I won't look up until I get to the other side.
I'm soon surrounded by people and only realise the traffic has stopped and it's my time to cross when they start streaming past me.
As I step forward, the experience quickly becomes unnerving - legs jump in and out of my vision without warning, while shopping bags fly towards my face before being pulled away at the last moment.
I'm sure I'm going to get hit, but after a few seconds I relax. It's OK. Everyone's reacting for me.
And then I realise there's two people who aren't. They're directly in front of me and they're not moving out of the way. I try moving left, but they do too. I swerve to the right, but they do too. We're stuck. It's so silly I have to look up.
I expect to see two dumbwalkers just like me. But instead I find a young couple, very much in love and very much refusing to let go of each other's hands just to get around an inconsiderate idiot on his smartphone.
The girl gives me a look of such contempt that I quickly apologise and rush round them. That look was enough to ensure I'll never be dumbwalking again.
智能机在日本的使用时间并不长，但是其蔓延速度之快—已经有超过半数的日本居民人手一部智能机。东京是一个拥挤的城市，已有警告指出在繁杂的人行横道上，大量的行人边走边操控着手机，是十分危险的行为。
现在是一个周五的下午5时，我站在世界闻名的岔口之一的涩谷十字路口上的一个咖啡店外。
这个地方每隔2分钟，就有超过千位穿戴整齐的东京上班族和青年弄潮儿们聚集在八个岔路口，准备通过马路，径直迎着对方急速而走。
看上去这些行人像要撞击在一起一样，而实际上他们像旋转的芭蕾舞者，绕过彼此，最终安全地到达对岸。
这情景如此令人惊叹，以致有时让人们（包括我在内）感觉到一些十分陈旧的理念，即：这景象多么完美的诠释了日本社会的理念—为了大众的福利而行动在一起。
但是我在这的原因，并不是为了留于惊异之中，而是希望可以看见人们撞在一起。
我想要看见商人们相互冲撞时他们的伞从手臂中飞出；看见那些纯真的、穿着校服的学生将奶奶绊倒。
为什么现在我可能看到这番景象而一年之前看不到呢？答案非常简单—都是因为智能手机惹的祸。
智能机的使用人数正在日本暴涨。2012年，只有四分之一的日本人使用智能机，那时大多数的人还十分满足于他们的日常手机。
但是人们现在意识到智能机的种种不容忽视的优势，尤其是能用来读报和看漫画，日本漫画早已走向全球，漫步到世界各个角落。
已经有超过半数的日本居民人手一部智能机，与此同时这个数量正在快速上涨。
此上涨还带来了另一种现象的产生，即：由智能机带来的低头行走一族。
人们只有在盯着手机屏幕时才采用这种冷酷如冰山的步调：低着头，伸出手臂，像一个想要猎食人类的僵尸一般。
日本的学者发现人们在玩智能机时不仅仅行走更为缓慢，他们的视角范围也降到了原本的5%，人们开始担心这种现象对涩谷带来的后果。
近期，日本手机巨头NTT多科莫公司发布了一个模拟实验，展示了如果每个过马路的行人都采用这种“低头行走”模式所带来的后果。
实验指出，每一次，过路的行人会有400多次的碰撞，而只有36%的人能够顺利通过马路。这样一来，我们所熟知的那个有序的日本社会将会走向终结。
然而令人惊奇的是，对此景象最为恼怒的竟然是美国人。
迈克尔·克拉克是一位顾问，住在日本已有20余年，在闲暇时间，他写了一个叫做“四国”的博客，最近该博客上杂乱地贴满了他称之为“低头行走”的内容。
这周，我在巢鸭见到了迈克尔，巢鸭位于东京，以其行走缓慢的退休人员而闻名。
他告诉我这种“低头走路”的现象不会是一个长远的问题。
日本的使用手机的礼节实际上比世界上其他地方要更好，在日本，几乎很少看到人在火车上打的电话，年轻人也不敢出于个人原因而外放音乐。
在涉谷，如果低头行走一族真的非常严重，警察就会开始在十字路口巡逻，呼喊人们抬起头来。然而，除非这种情况真的发生，警察才会转为大声咆哮。
但是，智能机所引起的行走方式真的会带来问题吗？只有一个办法来回答这个问题（那就是亲身实践）。所以我离开了咖啡店，走向十字路口，开始编辑邮件，我告诉自己，直到到达岸马路对岸才能抬起头。
我很快被人群包围，当人们从我身边涌动的时候，我才意识到车流已经停止，轮到我过马路的了。
随着我往前移动，我开始变得紧张起来--人们的腿毫无征兆在我眼前的跃来跃去，购物袋似乎差点要飞向我的脸上。
我知道我肯定会被撞击，但是不过一会我就放松下来。没事，他们都会对我有所反应。
同时我也发现了，有两个人是不会碰撞到的。这些人恰好在你的前方，同时也不会改变路线。我试着往左移动，他们也左移。我向右移动，他们也右移。我们被卡住了。我不得不抬起头来，这样看上去很傻。
我期待看到我和一样的两个低头走路的行人。但取而代之的是我看到一对年轻的夫妇，他们十分眷恋，十分抗拒仅仅为了绕开一个盯着智能机的傻子而放开彼此的手。
那个女孩轻蔑地看了我一眼，我赶忙道歉，匆忙绕过他们。那种目光让我十分明确：我以后再也不做“低头行走”一族了。