Before dawn, the teenage girls convened outside the Naples Navy base where the wildly popular Italian television show “Mare Fuori” is filmed.
“We want to show them all of our love,” said Federica Montuori, 16, who with her fellow fans unfurled white sheets with spray-painted messages expressing how the lead actors, who play star-crossed — and mobbed-up — lovers in a juvenile prison, “belong in our hearts.”
On the wall beside her, the scrawls on the bricks are love letters to “the most beautiful series in the world” and its main characters. “Ti Amo Carmine,” read one rectangle. “Ti Amo Rosa,” read another.
Other fans have dived from nearby piers and swum to the back of the set, vexing gate guards charged with keeping them at bay. During the day, their screams have ruined takes.
“We had to stop shooting,” said Ivan Silvestrini, the show’s director. “They won’t listen. It’s pretty unbearable, but what can you do?”
Italy has fallen for “Mare Fuori,” or “The Sea Beyond,” an often gritty but always soapy melodrama about the inmates of a coed juvenile detention center who pass the time stealing kisses — when not scowling at or occasionally stabbing one another.
Entering its fourth season, the show, set and steeped in Naples street life, is “Saved by the Bell” meets “Scared Straight” meets “Gomorrah” meets Skinemax. It has been a smash hit on Italian television and is a fixture on Netflix Italy’s most-watched list. During Carnevale, children dressed up as the precocious gangsters, with leather hot pants and jackets, tank tops, lots of chains and toy guns.
Its hypnotic theme song, recorded by an actor who plays an inmate on the show and who is also an increasingly popular singer in Italy, has been streamed 35 million times and gone platinum. Some fans have kept vigil singing the chorus outside the set.
The series tells the intertwining stories of a hodgepodge of attractive delinquents, in a fictitious juvenile hall inspired by a real one — where the sexes are separated — on an island off Naples. Most of the characters are hardened thugs from competing Naples mob families, but there is also a rich Milanese piano prodigy jailed after a night out in Naples goes terribly awry, and a manipulative goth goddess who licks faces, cuts herself and kills for fun.
The cast of mostly unknowns keeps the budget low, but the ensemble approach is also creating stars to supply Italy’s insatiable and often schlocky television-cinema complex.
The producers market the show as a dialect-heavy portrayal of Naples reality with a redemption message. But following on other Italian hits, like “Baby,” about underage prostitutes, the show has also underscored Italy’s infatuation with steamy young adult programming.
“We have realized that these stories of young lovers, people like a lot,” said Roberto Sessa, one of the show’s producers. “In the end, we are a romantic country.”
The plot revolves around Carmine Di Salvo, the reluctant and seemingly meek scion of a crime family who really just wants to be a barber, but who lands behind bars after stabbing a would-be rapist of his girlfriend in the neck with scissors. Incarcerated, he finds a nemesis in Ciro, the prince of the competing crime family, who eventually tries to kill Carmine and his piano-playing cellmate but who ends up getting stabbed with a screwdriver.
Things really took off in the third season, this year, when Rosa Ricci, the late Ciro’s sister, shoots a guy to get into jail so she can settle scores with Carmine. In classic Montague and Capulet style, she falls for Carmine instead.
On a street in Naples, a fan of the show, Domenico Marino, 18, and his girlfriend considered taking home a souvenir pillow — displayed next to similar shirts, mugs and key chains — of the scantily clad Rosa featuring her catchphrase (“I am Rosa Ricci, and who the [expletive] are you to tell me what I need to do”). He decided on a cushion of her late brother Ciro instead.
On Naples’s Via San Gregorio Armeno, famous for its Christmas Nativity scenes, a crowd gathered to admire terra cotta figurines of the cast standing in front of the juvenile prison, displayed next to a manger.
“We keep making them as long as there is demand, even for the ones who get killed,” said Elio Cassano, 60. “They don’t look at the soccer players or the Holy Family in the crèche, they form crowds around ‘Mare Fuori.’”
One of the admirers, Chiara D’Amico, 18, a Sicilian with a crush on Carmine, said the juvenile prison reminded her of high school. Her mother, Santina Santonocito, 40, said she liked the show because it taught children “not to make errors — life inside is not so easy.”
They were visiting Naples, with plans to see its castles and eat pizza. “But the first thing on the list,” Ms. D’Amico said, was a pilgrimage to the set.
Shortly before noon, a black van carrying Maria Esposito, 19, who plays Rosa, rolled up to the gate. She blew kisses from the passenger seat, sending the fans into a tizzy.
On the set — which looked like a seaside high school with a soccer court, a foosball table and a black piano that had hearts traced in its dust — she stopped in hair and makeup with Massimiliano Caiazzo, who plays Carmine.
“The theme of a forbidden love touches adults just as it touches adolescents,” said Mr. Caiazzo, 26, as Ms. Esposito, puffing on an e-cigarette, had her lashes doused in mascara.
She had worked as an aesthetician before she joined at the end of the second season, which had made her “weep perennially, every day, with joy.”
But for a young woman who loves going out (“I love living”), it was not easy being the face of Naples, she said. “I’m walking around the streets with my face on the pillows,” she said. “It’s a little creepy.”
The costume designer, Rossella Aprea, said that since there was no uniform in a real Italian juvenile prison, she could use her imagination. At a rack dedicated to Rosa, she held up a skimpy leotard decorated with dragons.
“A lot of black, super tight, crop tops,” she said. “Skin, skin, skin.”
Outside, the director struggled with a scene about the arrival of a new inmate, who held a leather satchel and looked as if he had either returned from safari or robbed a Banana Republic.
“Tell him to come out of the car and look towards the girls,” Mr. Silvestrini instructed with frustration. He said he understood sex appeal was vital to the show’s success and required the suspension of disbelief about love in the detention center through the creation of imaginary circumstances for hooking up, what he called “room for romance.”
“We created a pizza lab, a place where the boys and girls can be together,” he said. “And they can be promiscuous.”
After lunch, the director ordered the activation of a smoke machine for atmosphere, then walked a 40-something actor who played a crooked guard and a 20-something actress who played an inmate through their scene.
“Then, at a certain point,” he instructed. “The kiss moment.”
Their moment extended to a full-on make out session, lasting so long that members of the crew gave one another awkward looks.
Soon after, Ms. Esposito walked on set for the day’s final scene.
“She’s my star,” Mr. Silvestrini said.
Ms. Esposito, rail thin and with long straight black hair, wore bell-bottomed tight leather pants and a leather halter top. “These pants have gotten loose on me,” she said, laughing. “I’ve lost weight from the stress!”
She said everywhere she went, she was mobbed by teenagers, “but also the adults.”
“It’s in the hearts of all, this series,” Ms. Esposito said.
She and Mr. Caiazzo acted an intense face-to-face scene on a staircase, the director called it a wrap and the crew blasted the “Mare Fuori” song. Soon after, the stars departed in separate vans, and the fans screamed and ran after them.
Ms. Esposito made a heart sign with her hands.
“Rosa Ricci,” they bellowed. “Bellissima.”