Four male leads:
Go Go Squid 2: Appledog's Time - male lead Wu Bai gets teased for only ever wearing black, grey or white. And his outfits often have straps and buckles and other gamer-look elements. The overall effect is perfect for his character - a single-minded robot combat top competitor. (The drama has tons of product placements for German design house PUMA.)
Good Manager - male lead Chief Kim, full name Kim Sung Ryong, was in his element back when he was cooking the books for gangsters. But he had to quickly disappear. When he arrives in a slick corporate environment, he dresses in a way that shows he doesn't fit in one bit... and doesn't care at all. His suits scream with color and pattern, and he's not all that put together, all the time. It's so delightful seeing him thumb his nose at the corporate world!
Doctor Stranger - Male lead Park Hoon's perm - that perm! I can see it behind my eyelids! Totally on point character detail for a sassy, impudent outsider. The drama's kinda wack, but Lee Jong Suk is great in it.
The Sound of Magic - Magician Lee Eul dresses in a nonconformist way that reflects his identity as a dreamy loner.
Several second male leads:
Sweet Stranger and Me - second male lead Kwan Deok Bong is so well dressed it's intimidating, in his dandy suits, turtlenecks, and statement outerwear. When he dresses up, he rocks more than one loud fashion choice. This chaebol character gets a fair amount of screen time, and has a humorous, combative relationship with the tacky second female lead (she has more than one wardrobe item with fringe). Actor Lee Soo Hyuk is as gorgeous and laconic as ever.
Kim Ji Hoon, from my limited sample, might be the guy Hallyu calls when they need a character who's offbeat, with long or messy hair. Asian drama male characters almost always have neat, tailored and symmetrical short haircuts. And the sight of longer or messier hair has the same impact as a human billboard whose sign reads: "Look out for this guy! He's quirky!" Kim Ji Hoon's hairstyles are notable in these supporting character roles: (1) Love to Hate You, medium long and lovely locks for an expressive show biz type; (2) Flower of Evil, messy hair suggesting there's something more to his character than meets the eye; (3) Sweet Stranger and Me, that first episode proposal is mediocre - predictably, given his overgrown hair; (4) Flower Boy Next Door, I loved his messy, grunge-reminiscent hairstyle - and him - and mistook him for the first male lead. But I soon learned his hair was a sign his character was relegated to the second male lead zone.