ow, I know many things.

I know that caterpillars have 4,000 muscles. I know that one in twenty people have an extra rib, and that astronomers have discovered that sometimes on Uranus it rains diamonds. I know that camels originated in North America, that killer whales breathe in unison when travelling in groups, and that there are more receptor cells in a single human eye than there are stars in the Milky Way.

But I clearly know nothing about boys.

And right now I’d trade in every single thing I’ve ever learnt for just the faintest idea of what it is I’m supposed to do next.

I can’t sleep, so I wait until Rin is softly snoring, drag my duvet into the bathroom and curl up in the empty bathtub with my phone. It takes Nat a while to work out what’s going on. This is because I’m crying so hard all she can make out for the first three minutes is “S-s-s”.

“Spots?” she guesses, peering down the webcam. “Sausages? Socks?”

I shake my head. “S-s-s …”

“Sun cream? Scissors?” I can see Nat’s brain scanning through her vocabulary for anything that starts with an S. “Caesar Salad?”

A little bubble of unexpected giggle-snot comes out of my nose. I try something different. “N-N-N …”

“Nipples? Nits? No offence, Harriet, but it’s starting to feel like I’m trying to communicate with a penguin. Calm down and try to finish a word.”

I obediently wipe my nose on the duvet (oh, come on, as if everybody in the world doesn’t do that when they’re heartbroken). Then I take a few deep breaths and finally manage to hiccup: “S-sorry. I’m s-s-so s-s-sorry, N-nat. Y-you w-were r-r-right and I-I was wr-wrong and N-Nick d-doesn’t c-care about m-m-m-me and h-he h-has a n-n-new girlf-f-friend and sh-sh-she lives in m-my flat in T-T-Tokyo and sh-she’s b-b-b-beautiful and I-I d-don’t know w-what to d-do and I h-hurt a-all ov-v-ver a-and I j-just w-want to g-g-go h-h-home.” And I promptly burst into tears again.

Nat sits bolt upright. “What? He’s in Tokyo? You’re in Tokyo? Are you freaking kidding me?”

To say that I am not in the mood for kidding anyone right now is the understatement of the century. “I j-just s-saw him.”

Nat’s face disappears, and somewhere in the background I can hear things being zipped. I sniffle and wipe my eyes on a separate bit of soggy bedding. “Nat? Are you listening?”

“No.” Her head pops back into the screen. “I’m packing my bags and coming to get you.”

I smile. Toby was right: Nat is my non-kissing soulmate. I want things to stay exactly how they always have been: like salt and pepper, strawberries and cream, cheese and Marmite. Two halves of the same teddy-bear-shaped friendship necklace.

Although Nat might be being slightly optimistic. She has no transport and no money and she’s in deepest, darkest France. At 11 mph it’s going to take the poor pig nearly a month to get here.

“D-don’t be silly,” I hiccup, feeling a little bit calmer already. “Your mum will ground you for the rest of your life and then she’ll ground your ghost. I’ll be OK.”

Nat pauses, and then throws her passport on the floor with a frustrated growl. “Ugh. Seriously: what is wrong with boys?”

We both ponder this important question. It feels like one of the ancient, unanswerable ones. You know:

Why Are We Here?

How Big Is The Universe?

Is There A God?

What Is Wrong With Boys?

“S-s-so …” I sniffle on to my hand. “What do I do, Nat? Tell me, and this time I promise I’ll listen.”

We sit in comfortable silence while my Best Friend thinks about it. When we were little we would do this every time one of us fell over and scraped a knee, until it didn’t hurt any more. As if – just by being together – we could somehow share the pain. As if in some way we still can.

Finally, Nat makes a decision. “Pretend you don’t care, Harriet. Pretend you never have.”

I frown. “Nat … I didn’t even have the thespian skills required to play a tree in our Year Two performance of Snow White, remember?”

Nat laughs. “You fell off the stage and just lay there, waving your branches around until your dad came and stood you back up again. It was hilarious.”

It really was not. I couldn’t look Miss Campbell in the eye for months. She said I ruined the entire performance and maybe she would take that Drama job in Scunthorpe after all. “I don’t think I can do it,” I admit quietly. “It’s …” How do I even put this? “It’s Nick.”

“Which is why it’s even more important.” I can see Nat’s furious rash climbing up her neck again. “We can’t let him win. He’s not ruining this for you. Let me remind you, Harriet, YOU ARE MOD-EL-LING IN TOK-Y-O. You’re the luckiest girl ever. EVER. You pretend, and you pretend as hard as you can.”

This is all so confusing. One minute I’m being taught that lying is bad and I should never do it, and the next I’m being told to do it as convincingly as possible. Clearly when it comes to boys, every lesson I’ve ever learnt is supposed to be inverted. Why wasn’t there a class in this at school?

I cannot believe I wasted three years of my life doing woodwork.

“Harriet, listen to me. Will you please just trust me?”

I look at the floor and nod. If I had listened to Nat in the first place I’d now be two months into getting over Nick. I’d be much, much closer to being fine. “OK,” I agree. “I’ll pretend.”

“Good,” Nat says. “I didn’t want to be right, Harriet. I just didn’t want this to happen. I didn’t want him to hurt you.”

I’m so glad I don’t have to do this on my own.

“I miss you, Nat,” I say in a tight voice. “Can we never, ever fight, ever again?”

Nat laughs. “Of course we’re going to fight again. That’s what we do. I’m going to kick your skinny butt for the rest of eternity.” She looks at her nails. “Call whenever you need me. All I’m doing is trying not to milk cows.”

“Really? What’s it like? Is it all squidgy?”

“No idea. I keep telling people I’m not touching a cow’s boob like a big cow lesbian so I have yet to find out.” Nat grins and blows me a kiss. “This feels weird to say because it’s totally broad daylight here, but: go to bed, Harriet. Things will look better in the morning. They always do.”

I yawn and nod, suddenly feeling exhausted and drained. But also as if I’ve abruptly let go of something heavy. Or maybe something heavy has let go of me. By the time we say goodbye and I crawl back into my enormous bed – puffy but totally dry-eyed – I know exactly what my New and Infinitely More Glorious Summer Plan 3 (NAIMGS3) plan is:

Lie. Again.

This is my big adventure. I have travelled 6,000 miles and fifteen years to get here. I came to Japan to have the best summer of my life, and I am going to have it.

And no boy is going to ruin it for me.