Nearly four hundred years ago, in 1636, a strange edict was issued by Japan’s Tokugawa shogunate. ‘The whole race of the Portuguese with their mothers, nurses, and whatever belongs to them, shall be banished to Macao.’ The Portuguese empire had outposts across much of Asia at this point, Macao included. And almost no-one in Japan would have been able to point to Portugal itself on a map. This was the closest the Japanese authorities could get to ‘Portuguese go home.’

It was also ‘Christians go home.’ Japan’s Christian population had been steadily growing and their loyalties came into question. Did the latter point, ultimately, towards Kyoto or Rome? Christianity was banned and the edict offered rewards for anyone who caught a Catholic priest. It promised imprisonment, and possibly worse, for any person bearing ‘the scandalous name’ of Christ.

Christianity in Japan never recovered. The very idea that a single religious tradition might possess a monopoly on truth is widely regarded there as worrisome, even cultish. But Japan does do Christmas. It began to be celebrated shortly after Japan re-opened its doors to the West in the late-19^th-century. The result, by the early 1900s, was a Victorian-style affair indulged in by wealthier Japanese with a fashionable interest in western culture. Huge Christmas trees were placed outside department stores, plum pudding Christmas cake was sold and people puzzled over signs saying, ‘Merry Xmas.’

A few decades after the Second World War, fried chicken entered the picture. The manager of Japan’s first KFC overheard foreign customers talking about how they missed their Christmas turkey. He decided to launch a festive party barrel, and the idea achieved the 1970s equivalent of going viral. A tradition emerged of ordering special KFC Christmas dinners weeks in advance. Plenty more families, my Japanese in-laws included, buy and fry their own chicken on Christmas Eve.

Christmas in Japan is about romance, too. It’s up there with Valentine’s Day as a chance for young couples to enjoy an evening out, exchange gifts and pledge themselves to one another amidst great tangles of LED lights. Children meanwhile grow up confidently expecting the arrival of Santa – not via a chimney, since few Japanese homes have those, but rather by unlocking the door with magic (surely more likely and logical, for a man capable of criss-crossing the globe in a single night).

All this means that a lot less anxiety surrounds Christmas in Japan, compared with the Christian and post-Christian West. It’s always been about fun, shopping and atmospherics. There’s no hazy sense of deeper meaning, no well-spring that people need worry about tending or fear allowing to run dry.

New Year (shōgatsu: ‘the proper month’) is another matter entirely – mess with it at your peril. At the heart of this most important season in Japan is a turning from noise, chaos and disappointment towards serenity and a powerful sense of beginning again.

The season opens with companies wrapping up business deals, settling debts and organising alcohol-fuelled get-togethers known as bōnenkai. The word literally means ‘forgetting the year party.’ Everyone has done their best for 12 months, and regardless of the outcome, it’s done and dusted now. All that’s left is to forget. So important is this moment in the year that another feature of Japanese office parties, reminiscent of the old Roman Saturnalia, is allowed to come heavily into play: bureikō. As so often in this most logical of languages, the constituent kanji tell you all you need to know: ‘no’ + ‘manners’ + ‘association.’ Like ancient Roman slaves, company juniors may – within reason – treat their superiors in a way that would be completely unacceptable back in the office.

This is my favourite part of the turning of the year in Japan. In the West, we’re good at hoping for big things at midnight on New Year’s Eve – but less good at the work beforehand, of wiping the slate clean. That wiping, that purifying, receives a great deal of attention in Japan.

Alongside bōnenkai runs the eating of toshikoshi soba: long noodles, cut up to represent separating oneself off from the year that is passing away. The meal is eaten on New Year’s Eve, in homes that have been put through a deep clean-up and clear-out: getting rid of dirt, undesirable memories and unnecessary clutter from the year gone by. Toshigami-sama, the deity (or deities) of the incoming year, are then welcomed with decorations fashioned from bamboo, pine and straw rope. Brooms are safely stowed, lest someone should accidentally sweep away a visiting god.

New Year is the time when Japan’s Shinto underpinnings really reveal themselves. A still sense lingers, for some, that dirt will attract misfortune and that a break must be made with past deeds and misdeeds for fear of polluting the present and dooming the future. All this comes through in doing, rather than doctrine.

That includes the almost total shutting down of ordinary life for a few days from 1 January. In a highly-urbanised country, whose big cities really do never sleep, it always feels special – serene but also a little eerie – to find shops closed and streets quiet. The main reason people leave the house is to visit their local shrine for hatsumōde: the first shrine visit of the new year, asking the kami (gods) – whatever and wherever they might be – to look out for you and yours over the months to come.

Other ‘firsts’ are enjoyed. Hatsuhinode is the first sunrise of the new year, best appreciated from a beach, mountaintop or some other special place. Hatsuyume is your first dream of the year, in which you ideally want to see Mount Fuji, a hawk or an aubergine. This last may not sound like a very heroic theme for a dream. It’s thought to relate either to the word in Japanese (nasu) being a homophone for ‘achieve,’ or to the fact that once-upon-a-time aubergines were expensive and so dreaming about one suggests wealth. If instead you have a nightmare, you need only say upon waking: ‘I give this dream to the Baku’ – a creature in Japanese and Chinese folklore who devours bad dreams.

The symbolic seasonal dishes – osechi ryōri – meanwhile keep coming. Where Rome’s grand Saturnalian feasts were intended to suggest fertility and bounty, in Japan the symbolism is more targeted. A red sea bream called tai is eaten, because tai is part of the word medetai: happy, or auspicious. Sticky black soybeans, prepared in soy sauce and sugar, are enjoyed because the word for bean, mame, sounds like mamemameshii: diligent. Herring roe is on the menu because both in nature (fish eggs) and in name, kazu no ko, it suggests having lots of children.

No doubt more pleasing to most young Japanese than fish or beans is the prospect of shaking down relatives for otoshidama, new year’s pocket money, and tucking in to some mochi: sweet, chewy cakes. Making them is almost as fun as eating them. Some households do it in the traditional way, pounding rice using hammers and bowls. Others use machines that jiggle the mixture around in a rapid, mesmerising jelly-like motion, until it’s the right consistency for turning into cakes.

If ever someone manages to turn the Doraemon manga’s ‘anywhere door’ into a reality, I would attend a ‘forgetting the year’ party in Japan, spend Christmas in the UK and then slip back to Japan in time for the New Year build-up and celebration. Taken together – cleansing, Christmas warmth and a serene yet radical reset – it is hard to imagine a better way of easing the path from one year into the next.