You must be thinking of Lycoris squamigera.
They look very different than L. radiata, and much larger.
Also, bloom a little earlier in mid to late August in South Korea, while L. radiata blooms around mid September.
L. squamigera is also a lot more common since it can survive freezing winter, while L. radiata can not.
My grandma had tons of them in her garden, and it is a symbol of end of summer. Also, poisonous, so don't mess with the bulbs. lol