After succeeding in their winter conflict against Taiju Shiba and his Black Dragons, the Tokyo Manji Gang absorbs their group's remaining members. Due to his heroic courage and indomitable spirit, Takemichi Hanagaki should have accomplished his goal of defeating the tragic fate awaiting his girlfriend, Hinata Tachibana. In reality, Takemichi's troubles are far from over. Although Takemichi's actions have exposed Tetta Kisaki's treachery, the conniving schemer has found power elsewhere: Tenjiku, a dangerous gang led by the enigmatic Izana Kurokawa. Izana sets his sights on Manjirou "Mikey" Sano, pursuing a vicious interest in the Tokyo Manji Gang's aloof leader. In the future, Takemichi discovers that the machinations of Izana and Kisaki led to Mikey's moral ruin—a downfall that directly results in Hinata's death. Unfortunately, a terrible loss robs Takemichi of his time-leaping ability, stranding him in the past with one final chance to rescue everyone he loves.

Takashi Natsume has grown accustomed to his encounters with youkai through the Book of Friends, which contains the names of youkai whom his grandmother, Reiko Natsume, has sealed in contracts. These encounters allow Natsume to better understand the youkai, Reiko, and himself. 

The Book of Friends is a powerful tool that can be used to control youkai; it is sought after by both youkai and exorcists alike. Natsume just wants to live out his daily life in peace but is constantly disrupted by these experiences. If he is to end this torment, Natsume must explore more about the book and the world of exorcism, as well as begin to open his heart to those who can help him.

[Written by MAL Rewrite]

Subaru Natsuki finally gets to take a breather, but he does not waste any time as he prepares for a date with his beloved Emilia. He scouts the nearby village for the right dating spot, and with the help of the village children, he finds a wonderful location. With that, he is well prepared for his date! Unfortunately for Subaru, cold weather suddenly sweeps across Roswaal's mansion on his important day, leaving him with no choice but to postpone the date. Overnight, it becomes even colder and unbearable. Subaru must get to the bottom of this because, at this rate, his date will be the least of his worries.

In the future, water has covered much of the Earth due to the effects of global warming. The orphaned Maia Mizuki, 15, just graduated from middle school and has already applied for employment in the elite paramilitary Ocean Agency, part of the futuristic world government. Only the best, most intelligent, and physically fit students are eligible for admission. Maia, the series' protagonist, is set to become one of the few. But her ideal life quickly falls apart. To her disappointment, Maia unexpectedly fails her entrance exams. Making matters worse, she promptly gets evicted from her house, pick pocketed, taken hostage, then shot. She is "saved" by two women (Rena and Shizuka) that are part of an unorthodox help-for-hire organization called Nereids (inspired by the Greek mythological Nereids ). With nowhere to go, Maia joins up with Nereids, taking jobs from capturing wanted criminals to chasing stray cats, often with unexpected results. Gloria and Yu later join up with Nereids. "Daphne" in the title refers to a subplot that starts midway into the series and eventually become important to Maia. "Brilliant Blue" refers to the fact that this is a world covered by water with almost no land. The world consists of vast oceans, a few islands, and floating cities.