It’s known as higanbana in Japanese; red spider lily in English; Lycoris radiata in Latin.
It’s also referred to as manjusaka (曼珠沙華), based on an old Chinese legend about two elves: Manju guarded the flowers and Saka the leaves, but they could never meet, because the plant never bears flowers and leaves at the same time. They were curious about each other, so they defied the gods’ instructions and arranged a meeting. The gods punished them, and separated them for all eternity.
The flower is currently in full bloom in Tokyo.