It takes less than 10 minutes of watching the new “Heartstopper Forever” movie on Netflix to realize this is not the same tenderhearted romance to which audiences were first introduced.

When the British series debuted in 2022, Nick (Kit Connor) and Charlie (Joe Locke) were teenage boys of 16 and 14, respectively, navigating confusing feelings for one another in a show that was unabashedly sentimental and eschewed any references to anything even remotely sexual, cocooning the characters in flutters of animated love hearts. But the boys, like the actors who play them, have since done some growing up.

Their yearslong romance entered a new stage at the end of the third season, when they lost their virginity to each other. Now, having driven to a remote seaside pier at sunset, they race each other to the end and begin to passionately make out, before Charlize unzips Nick’s pants, sticks his hand down and goes to town. “I’m thinking about you,” the singer Baby Queen croons in the song that overlays the scene and title sequence, “and you’re thinking about sex.”

“We have this moment of just pure teenage abandon, teenage recklessness, which I think feels so real to teenagers,” said Alice Oseman, the writer of both “Heartstopper Forever” and the original webcomic-turned-graphic novel on which the series is based. “We have always tried to age up ‘Heartstopper’ a little bit every single time we come back to it.”