Yes, you can! Following is the Korea HOUSING LEASE PROTECTION ACT.
Article 6-2 (Termination of Contracts in Cases of Implied Renewal)
| (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.