Botanical: what are these flowers?

Commuting along the Tamagawa on weekdays, I couldn't help noticing these gorgeous, flaming red wildflowers that have sprung up during the past few days. They only seem to grow on the southern bank of the Tama (on the Kanagawa side) on a stretch about two kilometres long.

Can anyone identify them? What are they called in Japanese?

That's 彼岸花[higanbana]/曼珠沙華[manjushage].

Lycoris radiata - Wikipedia, the free encyclopedia
ヒガンバナ - Wikipedia

Red spider lilies, the harbinger of autumn. That was most interesting, thank you!