Unlike his twin brother, Yukio, Rin Okumura never wished to know about their parents and the circumstances surrounding his own birth. Yet the master of time, Mephisto Pheles, gives Rin a key that transports him 40 years into the past when his late mother, Yuri Frederick Egin, was merely a child. With Mephisto's guidance, Rin leaps through the years of Yuri's childhood and her adolescence as an exorcist-in-training. Early on, Yuri meets Shirou Fujimoto, Rin and Yukio's adoptive father. As Rin follows Yuri and Shirou's lives, he witnesses firsthand the initial appearances of Satan, his true father, and the horrors unfolding at the True Cross Order's special Section 13. Yuri's unique connection to Satan eventually leads Rin to the truth behind the most horrific event in exorcist history and the day he and Yukio were born—the Blue Night.

"How were Gaia Memories created?" "Why did W begin to fight?" To answer Tokime's questions, Shoutarou quietly begins to tell a story. He speaks of his meeting and parting with a man he admired and called his old man—his mentor, Soukichi Narumi. Mysterious people called Dopants, who utilized the powers of Gaia Memories, had begun appearing in the shadows of Fuuto, the windy city. A young Shoutarou had become an assistant of the detective Soukichi and, though called half-baked, began to follow in his footsteps. Unaware that, in addition to his detective work, Soukichi was secretly acting as Skull, Shoutarou began to grow frustrated with his mentor. That was when the Narumi Detective Agency received a phone call—a request from Hell inviting Shoutarou and company to a fateful night! When Shoutarou tracked down Soukichi to deliver the "trump card" bestowed by the mysterious caller, what did he see? Shoutarou and Philip. The one detective made of two and the night when Kamen Rider W began. That whole story will finally be revealed. (Source: Official site, translated)

As novelist Fuji is returning home in a rainstorm, her attention is caught by something peculiar: an animal resembling a dog asking her to take it in. Although she is reluctant at first, the animal impresses her by handing her an umbrella, resulting in Fuji welcoming the creature into her apartment. Soon, Fuji realizes that the animal is even smarter than she initially thought, as it begins communicating with her through writing. Whether the two are alone or hanging out with her family and friends, Fuji's new little friend never fails to entertain with its whimsical actions.