Yes, you can! Following is the Korea HOUSING LEASE PROTECTION ACT.
|(1)||In cases where a contract has been renewed pursuant to Article 6 (1), notwithstanding paragraph (2) of the same Article, the lessee may notify at any time the lessor of termination of the contract. <Amended by Act No. 9653, May 8, 2009>|
|(2)||The termination referred to in paragraph (1) shall enter into force upon the lapse of three months from the date when the lessor has received the notification.|
According to Article 6-2, the lease agreement can be renewed without any notification.
However, if you don't want to extend the agreement you should notify the landlord at least 2 months ahead before the agreement ends. If you don't the lease agreement will be deemed to be renewed automatically.