The Dragon's Precious Princess

When three royal siblings trigger an ancient curse by trespassing on monster lands, their selfless sister willingly offers herself as a sacrificial bride to save their lives. Instead of meeting a gruesome demise, she is pampered and revered by the formidable beast. Upon returning to her homeland, however, she receives no warm welcome. Her ungrateful brothers have embraced an opportunistic newcomer, lavishing affection on the scheming imposter while treating their savior with cruel suspicion. When the deceitful substitute fabricates a lethal ailment demanding the true princess's living heart, her treacherous family prepares to discard her once again.