The consent of the assumption of the obligation by the obligee shall, if there exists no different declaration of intention, be effective retroactively as from the time of such assumption; provided, the retroactive effect may not harm the rights of a third person.
Civil Act — Article 457 (Retroactive effect of assumption of obligation)
민법 제457조
For AI agents and developers — get this article as JSON, with the English and current Korean effective dates and an outdated-translation flag, from the korea-law API or as an MCP tool:
https://mcp.apify.com?tools=kr-data/korea-law