The judgment below is reversed and the case is remanded to Seoul High Court.

The grounds of appeal are examined (to the extent of supplement in case of supplemental appellate briefs not timely filed).

1. Article 3(3) of the Act on the Regulation of Terms and Conditions provides that “The business entity shall explain important matters of the terms and conditions so that customers can understand them.” Article 3(4) of the same Act imposes a specific and detailed explanation obligation on the important matters of the terms and conditions on the business entity, and Article 3(4) of the same Act provides that when the business entity entered into a contract in violation of the obligation to explain the terms and conditions, it may not claim the content

"Important content" subject to the duty to explain refers to a content that a customer may directly affect the conclusion of a contract or the determination of the price in light of social norms.

(see Supreme Court Decision 201Da69053, Feb. 15, 2013). Demanding a business operator to explain the terms and conditions is based on the following: (a) the customer is not aware of the content of the terms and conditions; and (b) the customer is subject to unexpected disadvantages.

Therefore, even if the terms and conditions are general and common in the transaction, if it is a matter that could have been sufficiently anticipated by the customer even without a separate explanation or is merely a matter that is merely a matter that is already determined by the laws and regulations, it cannot be said that the business operator has an obligation to explain such matter.

(see, e.g., Supreme Court Decisions 2013Da217108, Jul. 24, 2014; 2016Da277200, Jan. 17, 2019). The requirement for “general and common terms in transaction” as a ground for exempting a business entity from the duty to explain is a customer in terms of whether the relevant terms and conditions are generally used in the transaction system.