In her tiny sunlit Seoul apartment, Kim Jeong-ran sat on her bed, talking affectionately to a cloth doll perched on her lap. “Hyodol, you’re my lovely granddaughter,” the 81-year-old said, cupping the doll’s stubby hands. “I love you to the moon and back.” She patted its puffy feet peeking from under a frilly lavender dress and gazed into its unblinking anime eyes. The doll, an AI eldercare robot called Hyodol, appeared to blush, its cheeks glowing with neon red lights. “Grandma, I miss you even...