Ichiya Chitani (Taiki Sato) made his debut as a novelist when he was in middle school. His novels received severe criticisms and were not popular. Now, Ichiya Chitani is a high school student. His confidence as a writer is shot. One day, an editor proposes that Ichiya Chitani collaborate with his classmate Shiina Koyurugi (Kanna Hashimoto), who is a popular writer, on a novel. The editor wants a novel that can touch the hearts of people around the world. Ichiya Chitani and Shiina Koyurugi have completely different personalities and reside on different levels in terms of popularity as writers, collaborate on a new novel.

The main character, Baian Fujieda, is a dark hero who has two faces: one as a skilled acupuncturist who saves lives, and the other as a criminal who buries evil that cannot be kept alive for the sake of others. Popular writer Shotaro Ikenami's historical novel series of the same title, on which the film "BAIAN The Assassin, M.D." is based, is a blockbuster bestseller with a total of over 6 million copies in print and has been made into a timeless entertainment film many times in Japan. Many famous actors have played the role of Baian, including Ken Watanabe. The year 2023 marks the 100th anniversary of Shotaro Ikenami's birth. In the anniversary year of 2023, a new "BAIAN The Assassin, M.D." is born.