Manga by author Yoshida Motoi - Status ongoing

Narumi Rokurou is still adrift in life in his forties, unmarried, and working as an editor at a publishing company while writing hardly lucrative literary fiction. His days enjoying life at his own pace are brought to an end one summer night, when a strange twist of fate brings Rokurou together with a mysterious beauty, beginning the story of their crazed love. As once was spoken by Zarathustra: "Everything in a woman is a riddle."

Nanoka and Koshiro were separated at a young age when their parents divorced. Now, 10 years has passed, Koshiro has already forgotten about his younger sister. Yet, Nanoka has decided to attend the nearby high school and came back to live with her father and brother. However, the two have met just before Nanoka came back to live together and without knowing each other's real identity, they went on a date, only to find out that they were actually siblings...