Kō Nikaido (stylized as Ko Nikaido) is a Japanese manga artist known for creating the series With You and the Rain. The creator's birthday is February 16. Nikaido began publishing manga in the mid-2010s, with early credits including contributions to anthology series such as the yuri drill line of books released by Kadokawa. Other early works include the series Hime no Dahan, which ran in 2016, and the short story collection Say Thank You, released in July 2020.

Nikaido is best known as the author and illustrator of With You and the Rain, known in Japan as Ame to Kimi to. The manga is a comedy series that follows a young woman who adopts a peculiar creature that insists it is a dog. The series began serialization in Kodansha's Weekly Young Magazine, a seinen manga magazine, on August 17, 2020. Kodansha has compiled the chapters into individual tankobon volumes, with the first volume released on March 5, 2021. The series is licensed for English digital release in North America by Kodansha USA.

In August 2024, it was announced that With You and the Rain would receive an anime television series adaptation. The anime premiered in July 2025, produced by the animation studio Lesprit. The series was nominated for the 2022 Next Manga Award in the print manga category.