unty and Wilbur don’t leave my side for the next twenty-four hours. It’s no longer my New and Infinitely Less Glorious Plan 3 (NAILGP3).

It’s theirs too.

They take me for slightly rubbery sushi from a conveyor belt. They take me to see a Hollywood blockbuster at the Waseda Shochiku Cinema. They follow me to the Meguro Parasitological Museum, and then promptly go outside to vomit (it has the longest ever tapeworm found in a human: it’s nearly nine metres long).

By the time I meet Wilbur at Tōkyō train station the next morning, I’m pretty sure that one of them is standing outside the bathroom every time I go to the toilet, just to make sure nobody’s followed me in.

“Cooo-eeeee!” he screeches across the enormous, incredibly busy concourse, pushing his way to meet me. “Over here, my little Chicken McNugget!” He’s wearing a bright pink suit with sparkly wings drawn on the back, and a leopard-print cap. “Back to genius attire, I’m incandescent to see.” He looks me up and down. “What’s the inspiration this time, Buttercup?”

I smile. “My father made it for me.”

Wilbur looks carefully at my denim dungaree dress, stripy leggings, neon-green trainers and the white T-shirt with the huge word MODEL written on it in red marker pen.

Let’s just say: Dad finally noticed my satchel.

“My Father Made It For Me,” he sighs happily. “You light up my life, Sugar-lump. You really do.”

Bunty nods from behind me. “Your turn,” she says, pushing me gently towards him.

“Got her,” he says, grabbing my arm as if we’re playing Harriet Relay. “Go home and guard those two backstabbers.”

“On it. Poppy’s having a bath, and I may or may not have propped a chair outside the door. Rin’s trying to train her cat to roll over, so that should keep her occupied for the rest of the day.”

“Just don’t let them leave the house,” Wilbur says, and then blows my grandmother a kiss and starts leading me through the train station with his arm tucked through mine as if we’re two teenage girls, not one and a slightly portly fashionista.

I assume we’re going on the metro, and am already weak with relief that it’s not rush hour so we won’t be physically crammed into a carriage by a little man wearing little white gloves and a hat, like a really aggressive Fat Controller from Thomas the Tank Engine. But Wilbur steps on to the up escalator.

“The shoot isn’t on the underground?”

Wilbur tinkles with laughter. “You think we’d risk making you stand up on a moving vehicle?”

OK, I asked for that. “So where are we going?”

“Think about Yuka’s subverted thingummy-jiggery. You’re a smart cookie, Coffee-bean, why don’t you tell me?”

The butterflies in my stomach go completely bonkers.

“Mount Fuji?” I squeak, gripping his arm. “We’re going to Mount Fuji?”

At that precise moment, we get to the top of the escalator and Wilbur points at the instantly recognisable, long, shiny white train pulling into the station.

A pointy-nosed train with a blue stripe running down the side of it.

The most famous train in the entire world. Apart from Thomas, obviously.

“We certainly are,” he says, patting my head. “And we are getting there on that.”

The first time Dad brought Annabel home, she brought me a book about mountains. Everest. K2. Kanchenjunga. But Fuji was always my favourite because – unlike the others, hanging out in the Himalayas – it didn’t have any friends.

I guess I felt a certain empathy with it.

In a flash, I suddenly understand what it is Yuka’s doing. She’s using fashion to challenge cultural stereotypes: living fish in a dead fish market. Women on a sumo stage. People trapped inside a computer game instead of by it.

The more I know Yuka, the more I admire her.

It’s just a shame the feeling is almost definitely not mutual.

Wilbur and I wait by the smooth white electronic barriers that stop people climbing on to the track. Then we clamber up the stairs on to the Shinkansen and take our seats. I’m so excited, if the windows opened I’d be like Hugo on long car journeys: head out, tongue halfway down my chin, drool hitting the unlucky person behind me.

“By 2008 these Bullet Trains had made enough trips to circle the earth 30,000 times,” I tell Wilbur breathlessly.

“At top speed it takes a train three minutes and 45 seconds to stop,” I inform him as the train starts gently accelerating.

“In 47 years there have been 7.1 billion trips made on the train, and never a fatal accident,” I say as a beautifully dressed woman in a hat and gloves starts walking down the aisles with refreshments, like an air hostess from the 1950s.

“Ooh, peanuts,” I add happily.

As we slide out of Tokyo, everything slowly changes. The buildings get smaller and smaller, and the gaps between them get bigger and bigger. Suddenly – with an almost audible pop – there are big green stretching fields and tractors and little squat houses with peacock-blue tiles on the roof and dogs barking. The ground gets very flat, the sky gets close and bright, and there are people: bent over, wearing big flat hats and picking rice. We’re going so fast that I’m literally pinned to my seat: my entire body is heavy and I have to pull myself down the aisle to the toilet like a little tree-swinging monkey.

There’s a sudden peace, and for the first time in days I feel like I can breathe.

The only thing I can’t really wrap my head around is how everyone else on the train can be so nonchalant. In fact, the majority of the people on here are actually fast asleep: eyes rolled back and heads lolling against the people sitting next to them.

“People can get used to anything, Possum-breath,” Wilbur says quietly. “You don’t go into raptures every time you see the London Eye, do you?” Then he raises an eyebrow. “Actually, my little Kidney-bean, you probably do.”

I look at my lap. Well, it is the world’s largest cantilevered observation wheel.

Fifty minutes and six hundred breathless observations later, the train stops and an electronic voice says in a cut-glass American accent: “Now arriving at Shin-Fuji station.”

“Is this it?” I burst out, standing up too quickly and smacking my head hard on the overhead compartments. Ouch. “Are we here? Are we at Mount Fuji? Can I see it? Can you show it to me?”

As if it’s a shy kitten, and not a volcano 3,776 metres high.

“This is us, my little Butternut-squash,” Wilbur says, then he points out of the window. “And who’s that?”

I turn, but even as I’m turning I know, because Wilbur’s got that twinkle.

That Well-What-Do-You-Know twinkle.

That What-A-Coincidence twinkle.

That Fairy-Godmother-Before-The-Ball twinkle.

That One-Day-I’m-Going-To-Get-Shot-By-Harriet-Manners-And-It’ll-Be-All-My-Own-Fault twinkle.

My eyes meet Nick’s and every single one of the one hundred trillion cells in my body leaps into the air. With difficulty, I lift my hand. “Hey,” I finally mouth through the glass.

“Hey,” he mouths straight back.