Acne may have its big-boy bona fides in order—international distribution, its own literary journal, the occasional show in Kensington Palace, even a much-touted collaboration with Lanvin before its fellow Swedes at H&M reached the atelier d'Elbaz—but it's always pitched itself as the label of guys just wanna have fun. And then its Fall collection emphasizes the suit?

"It's just a feeling, you know," creative director Jonny Johansson shrugged after the show. "All the tailoring—I thought that was in the moment, something fresh. I'm tired of all this heritage, the older models or whatever. It's time for something young."

That translated into a series of overcoats paired with suit pants, as well as the two-piecers themselves. The idea of a man's first suit is one that's been gripping other designers during this very sartorial season—Kris Van Assche, for example, was mulling it, too. It's also good business, especially at Acne's relatively modest price point: The suit revolution of the past few years has trickled down to the younger generation, and it's labels like Acne to which they'll turn.

The Acne cut is youthful, with slightly cropped pants and low-buttoning jackets in different styles (single- and double-breasteds, standard lapels and shawl collars), all in Italian bonded wool. The hitch is that, on the runway at least, they can look a little flat, even when pepped up by accents of raspberry, royal blue, or teal. "It's the way they dress," Johansson said of his clientele. "It's that moment when you're not grown up and at the same time, not a kid. The kind of sexual energy that brings." Keep looking down, to the boys' shiny patent Chelsea boots, and you could get a better sense of the signature Acne charge.