Slime Jeunghugun

A strange catastrophe has struck the world, turning people into slimes. Min-Ha secretly takes her sister, who has turned into a slime, and sets out on a journey. Their destination is the one place her sister had always longed to visit. Along the way, as she encounters people who still hold memories of her sister, Min-Ha begins to confront the unfamiliar truths about the sister she once loved.

(Source: Naver, translated)