The title comes from the cheerfully inescapable Bobby Hebb song — "Sunny! Yesterday my life was filled with rain" — although it’s been remixed and K-popped into a high-pitched disco melody.

It’s also the gang name for seven South Korean high school girls who band together, apparently, simply for the fun of banding together. They dance, they chat, they face off with other girl gangs. They don’t really have much in common otherwise. Even so, the experience of getting to know each other shapes them.

They grow up and they grow apart, particularly after a shattering experience in a school talent show. Years later, one of the members stumbles into another at a hospital and decides to get the old gang together. She looks back on her high school experience as a glowing time in her life, despite the fraught emotions and dreadful game-playing. Things are certainly looking a little gray as the girls enter middle age and encounter mortality.

Like John Hughes’ teen movies, "16 Candles," "Pretty in Pink" and "The Breakfast Club," this film treats the adolescent experience with respect, leavened with knowing humor. Much of "Sunny" is very funny, all the more so because there’s an underlying backbone of serious intent. It’s mostly successful at balancing the two into a bittersweet, rueful memento mori.

The intercutting of past and present is skillful and meaningful in ways that advance our understanding of the characters. "Sunny" does suffer a bit from the Korean penchant for hand-wringing melodrama, although — practically in the first scenes of the movie — it also satirizes it.

Writer-director Kang Hyeong-Cheoi has a keen grasp of what motivates teenagers, which is mostly a desire to be an individual while also being like everyone else. In "Sunny" there’s a lot of talk of double-eyelid surgery and Nike logo lust. And that’s another reason it seems so Hughes-ish. It’s set firmly in the 1980s.

The movie also uses out-and-out cursing as a comic tool better than any movie in memory. A director’s cut recently opened in South Korea, where the movie is a hit, which restores 10 minutes of girl fighting and profanity.

As adult Na-Mi, Yoo Ho-Jeong is adorable and a bit frazzled; she’s rather like a Korean Mary Steenburgen. She manages the difficult bit of eliciting empathy for a character who has gone from duckling to swan, seemingly has it all and yet yearns for her duckling days. As teen Na-Mi, Shim Eun-Kyeong is a fresh comic face, and the world’s worst dancer. They’re all upstaged by Ko Su-Hee as a size-large insurance agent with dreams of double eyelids.

"Sunny" is a monster hit in South Korea, one of the biggest movies of the year.

Although it looks back on adolescence with good humor, the film doesn’t forget that for most people the teenage years are the most vivid period of their lives, the most exciting, the most frightening, the most glorious.

And then it inevitably goes away, swallowed up by gray adulthood.