Hyunsik, aged 28 is a singer, composer and director in South Korea who sometimes sick from mental disorder. This sick would causes he easily unable to think and act reasonable,logical and rationally. He also easy to hallucinate when alone.

One Dis 20, he entered into an contract and agreement with Lee Chang Won to sell he land heritage in Gwangju for 3.5 million won. Without know the current market value, he decide to sell that land. Unfortunately, the current price market are more higher than he sell. The current market value of the property is 17 million won. A three days later, he realized the real current market value. He think that he would suffer lost due to the contract.

He decided to know whether he could challenge the validity of the contract.

Discuss the contractual rights and liabilities of Hyunsik.