By Jessie Yeung, Yoonjung Seo, Gawon Bae, Mike Valerio and Lauren Kent, CNN

Seoul, South Korea (CNN) — Opposition leader Lee Jae-myung was sworn in as South Korea’s next president on Wednesday following a dramatic snap election six months after the country’s previous leader declared martial law and plunged the nation into chaos.

Official results showed Lee winning by nearly three million votes ahead of his main rival, Kim Moon-soo of the incumbent conservative People Power Party.

Kim conceded defeat early Wednesday morning, congratulating Lee on his victory in a speech and saying that he “humbly accept(s) the people’s decision.” Addressing crowds of supporters in Seoul, Lee promised to “work to restore the economy” from day one and to ensure there will never be a military coup.

Lee was

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