His popularity skyrocketed when he starred in hit period drama Moon Embracing the Sun,^[16][17] which was number one in its time slot and at its peak recorded viewer ratings of 42.2 percent.^[18][19] He again contributed his vocals to the soundtrack, the traditional ballad "Only You" which topped digital music charts,^[20] and the more modern in composition "Another Way" released as a "Secret Version" single. He later won Best Drama Actor at the 2012 Baeksang Arts Awards, a win which was hotly debated as he was the youngest and newest actor among the nominees in his category, beating heavyweight veterans such as Han Suk-kyu, Shin Ha-kyun and Cha Seung-won. Upon receiving the trophy, Kim said, "I am very grateful for this moment, but I am ashamed as well. It’s like getting a lot of homework. I’ll keep trying to become a better actor in order to remain worthy of this award."^[21][22]
Since the success of Moon Embracing the Sun, Kim has set a new record for product endorsements by being the face of 17 products simultaneously, including a laptop, a camera, suits, cosmetics, sportswear, outdoor goods, a coffee franchise, pizza, ice cream, jelly, softdrinks, beer, fabric softener and a telecommunications company. According to entertainment industry insiders, Kim would have earned more than 6 billion won ($5.3 million) from his exclusive deals (most Korean A-list celebrities are said to earn 300 million to 350 million won).^{[23][24][25][26]}
Kim made his big-screen debut in the star-studded heist film The Thieves, touted in the press as the Korean version of Ocean's Eleven. His character Jampano is the youngest member of a gang of Korean and Chinese thieves who team up to steal a diamond worth 40 billion won locked away in a casino in Macau.^[27][28] After joking that it helped him to focus on the role and the kissing scenes since his partner was Jun Ji-hyun, Kim said he was overwhelmed to be around so many big stars and felt lucky to be part of the film.^[29]
His casting has been announced for the upcoming Secretly, Greatly. Based on the comic by Hun, it follows the story of Won Ryu-hwan, the leader of a group of North Korean boy spies known for their handsome looks. Won has the ability to read people but acts like a countryside fool as his cover; his journey begins when he is abandoned by the North. It is currently in pre-production and is set to start filming in July 2012.^[30]