A wise man once said, “Everybody’s got a hungry heart,” and they don’t get much hungrier than Minnie Goetze, the wide-eyed 15-year-old at the center of Marielle Heller’s intoxicating debut feature, The Diary of a Teenage Girl. An aspiring cartoonist with a burgeoning appetite for love and sex, she froths at the mouth for her first taste of sexual awakening, her art a full expression of her obsession with the human body and its nether regions. Her hormones bubbling and her curiosity overflowing, she latches on to the closest hunk of manhood she can find, who just happens to be her mother’s 35-year-old boyfriend, Munroe. As Minnie zooms down the fast lane to womanhood with reckless abandon, we clutch our hearts and hold our breath, waiting for the impending crash and burn.

Minnie’s played by Bel Powley, a short actress with Matryoshka-doll features who’s physically dwarfed by most of her co-stars but gives the most towering performance of all. Kristen Wiig plays Minnie’s unwatchful mother, who drinks incessantly, smokes pot, snorts cocaine and leads her own life as Minnie and her other daughter, Gretel (Abby Wait), float through life without proper supervision.

Without a guide to set her straight, Minnie mistakes the handsome Munroe (Alexander Skarsgard) for a full-grown man when, on the inside, he’s a broken boy who’s just as lost as she is. They use each other for sex and consolation, neither of them mature or strong enough to put a halt to the regrettable affair. The most interesting of the movie’s many wrinkles is the gigantic size difference between Powley and Skarsgard. She’s incredibly tiny and girl-like (Powley was actually in her early 20’s during filming) and he’s incredibly tall and manly, a disparity that makes the age difference all the more staggering.

The movie’s set in the San Francisco of 1976, a time when free love and bohemian frivolity were so prevalent that it was almost fashionable to brush off parental responsibility. It’s critical to the story that it take place when and where it does because the touchy, Lolita-esque scenario at the heart of the plot would have been much more incendiary had it taken place just a decade before or after, or even in the present day. It just doesn’t feel right to mention pedophilia in any discussion about Diary because Heller doesn’t participate in any kind of blame game; she presents the story from Minnie’s perspective exclusively, and since she’s in no state to judge Munroe’s behavior. In her eyes, he’s her one-way ticket to adulthood, not a creepy older man. If the movie were about him, he’d have been put on trial, but it’s not. It’s Minnie’s diary. Whether we judge or not is completely left to us, an artistic choice that’s in good taste. Morality isn’t on the agenda here; authenticity and truthful emotion are.

The movie’s adapted from a graphic novel of the same name, written by Phoebe Gloeckner. Heller doesn’t shy away from the material’s illustrated roots, occasionally populating the screen with hand-drawn figments of Minnie’s imagination, colorful cartoons in the vein of the early days of Disney animation. The primary manifestation is an illustrated fairy godmother named Mrs. Crumb, an imaginary version of Minnie’s favorite feminist cartoonist. Aside from these wondrous flourishes, Heller captures the essence of San Francisco—in all its sun-gold, hilly glory—like few movies set in the city ever do. It’s a magical city, and its greatest charms go unnoticed too often, but Heller, a Bay Area native, gets it right for once.

If you feel uncomfortable watching Diary, you could hardly be blamed. Minnie and Munroe’s romance isn’t easy to digest out of context, but Heller presents it in a way that allows you, if you’re willing, to free yourself of the scenario’s taboo implications. The movie isn’t erotic or salacious in the slightest. It’s actually pretty funny, and the humor is mined from Minnie’s naive teenage perspective. The movie opens with her narration as she exclaims, “I had sex today!” Heller films her walking through Golden Gate Park as if she’s 7 feet tall, pointing the camera up at her rear end as she stomps around, proud of her sexual conquest. The harshness of adolescence is an ugly thing sometimes, but it’s silly and absurd at the same time.

Jack White said of his former White Stripes counterpart Meg White that he hired her for the childlike way she banged on the drums. Her exuberance was loud and untameable, and Powley exudes that same primal, unteachable energy as Minnie. She’s unpredictable, rough around the edges and gripping in her every move. Her raspy voice draws you near and her saucer eyes keep you close.

Female adolescence is a topic rarely covered with as much dimension, truth and empathy as Heller’s Diary. And let’s not downplay the fact that this is as much a comic book movie as The Avengers, Batman v Superman and all of those other superhero movies that people site when dismissing comic books as “just for kids.” If you watch and enjoy Diary, do yourself (and me) a solid and pick up Gloeckner’s graphic novel. You won’t regret it.

The coming-of-age genre’s tropes have become so ubiquitous that chances are when you read a title like The Diary of a Teenage Girl you’ve already anticipated her sexual awakening and an unhealthy romance. This film has those beats, but Marielle Heller’s debut feature film comes with so much more. Mostly, it’s the authenticity of 15-year-old Minnie’s voice (played by newcomer Bel Powley).

Writing and directing an adaptation of Phoebe Gloeckner’s novel of the same name, Heller includes several animated sequences from Gloeckner’s graphic illustration style, which are peppered through the movie. Minnie endearingly and hilariously spouts her limited wisdom into her audio diary, which serves as the movie’s narration. She tells herself, the diary, and us, “It felt so good to imagine he might be thinking about me.” They’re such well-observed statements, so clearly the reflection of an awkward but thoughtful adolescent mind.

Early on, Minnie becomes involved with her mother’s boyfriend Monroe (Alexander Sakrsgård), a man 20 years her senior. At first he’s her vehicle for escaping the isolation of virginity. As the movie continues he becomes her gateway to further sexual exploration and drug experimentation. Part of what’s refreshing in The Diary of a Teenage Girl’s approach is we don’t feel the film judging Minnie for any of these actions. She retains her agency, and pulls herself out of her stupor. She’s a girl being confronted with the realities of adult life and the consequences of her actions.

As the Opening Night Film for New Directors/New Films, it’s fitting that The Diary of a Teenage Girl comes from such an exciting voice. Heller’s film brings life to a story that could have otherwise felt tired, and portrays its characters with such honesty that their emotional arcs are felt. Minnie Goetze is bound to become a favorite movie character for teenage girls, but she’s also one of the most fun, easy to root for protagonists of any film in this festival.