'To All the Boys' Author Jenny Han Says Lara Jean and Peter Are All 'Grown Up' in Final Film

Lara Jean and Peter are all grown up.

Fans of To All the Boys I've Loved Before have been enthralled with the teen couple's love story since the first film in the trilogy dropped on Netflix in 2018.

Now, with the third movie streaming on Netflix, the author behind the books on which the films are based tells PEOPLE that viewers may be surprised by all of the emotion in the final installment. Lara Jean (Lana Condor) and Peter (Noah Centineo) are becoming adults — and their relationship is about to face its biggest challenge yet.

"It might feel a bit more grown up because there's a lot of emotions," says author Jenny Han. (On Monday, it was announced that Han will serve as executive producer and co-showrunner of the Amazon adaptation of her YA novel, The Summer I Turned Pretty.)

"I teared up a couple of times watching it," she continues. "It feels like there's been a progression with going from a flirty, kind of fake relationship to the real deal. What is it like to be really in it with somebody and to face these challenges together?"

To All the Boys: Always and Forever follows Lara Jean and Peter as they wait for their college acceptance letters. Their life plan immediately starts to shift when Lara Jean gets admitted into New York University and her dad, a longtime bachelor, pursues a romance of his own.

In PEOPLE's chat with Han, she explains what it was like to finish filming during the COVID-19 pandemic, the magical chemistry between Condor and Centineo ("Their chemistry is undeniable," says Han) and Lara Jean's unexpected second love: New York City.

Keep reading for more from the bestselling author and producer.

PEOPLE: How did the pandemic impact filming?

Han: In Canada, you have to quarantine for two weeks when you get there... it's hard for people with families because you're going to be away from them for a long time. For me though, I've been just really busy. I feel like this has been a really fertile time for me to be kind of working in the lab writing. I'm excited to be able to share the movie. We've been working on it for so long and now to finally be able to share it with the fans, it's really exciting.

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What was the chemistry like on set, especially between Noah and Lana?

Their chemistry is undeniable. They really spark to each other on camera and I think they really have a rhythm with each other... They have a shorthand with each other because the experience has been really unique for both of them. To be able to share it with each other has made them trust each other more... My favorite scenes in the film are always with the two of them.

In what ways has Lara Jean and Peter's relationship grown compared to the last two films?

They are not afraid to be vulnerable with each other. As the characters have grown and matured and come into their own, they've allowed themselves to do that in their relationship as well. For Peter, it's harder for him to be vulnerable or to say what he really needs in the relationship because he's often been very focused on what Lara Jean needs. The third film really explores that. For Lara Jean, she starts out the first film as being someone who likes the security blanket of being with her family and being at home. She steps out further by the third film. We see her exploring new cities and trying things that she never would've tried a couple of years ago. She's being brave and taking those chances, but still being really true to herself.

What types of challenges and tensions will they face as they decide where to go to college?

They're both going to have to decide what is right for them. You decide that and then you cross your fingers that it will also be what's right for the relationship... It's like putting your own air mask on on the plane first. Only then can you be good in a relationship.

In the first film, it starts with Lara Jean being a bit judgmental about Margot's decision [to go to college in Scotland] and saying, "I would never do that. I would never leave my boyfriend. If I really loved him, I wouldn't do it." I think she feels really certain. Part of why I wrote the third book was because I wanted to put her in the exact same shoes and say, "Okay, what would you do?" You think you know what you'll do in a moment and then you're really there and you're not so certain anymore. So, it really is coming full circle.

Lara Jean falls in love with New York City unexpectedly. What about the city draws her in?

For someone who is a writer, I think there's no place like New York because the city is the story. The city is its own character. It has this rich history and you can't help but feel really creatively energized and drawn to this place that has stood the test of time. For Lara Jean, it's really unexpected. She's this girl who is a homebody and likes to be cozy. She didn't really expect to come to New York and feel so swept away by it.

Do you have any favorite behind-the-scenes moments from filming?

Lana and I were up on the rooftop for the party scene. We look across and we see that the Empire State Building has been lit up for us. That was probably the most exciting thing for me and you can see it in the movie. New Yorkers always look at the colors and wonder why there are certain colors at night and it was like a juicy little secret that we had when we were filming that night in New York. It was for To All The Boys. The colors were pink, yellow and blue.

We get to see more of Lara Jean's sisters and dad in this movie. What do you want fans to learn about family?

If there was anything I wanted young people to take away from the stories, it would be that your family is going to keep changing over and over again in your life. It doesn't stop when you're an adult. Your parents will pass away, or you'll get divorced, or there'll be new life. It's something that we all have to go through. But it doesn't have to be a bad thing — it can be really beautiful.

This interview has been edited and condensed.