In the future, water has covered much of the Earth due to the effects of global warming, leaving the human race to live on neighboring floating cities.

The orphaned Maia Mizuki, fifteen years of age, just graduated from middle school and has already applied for employment in the elite Ocean Agency, part of the futuristic world government.

This subplot that starts midway into the series concerns Maia's journey to retrieve a time capsule of her past buried under a laurel tree in Elpida, an undersea city lost over a century ago.

(NIV) The manga of the series is a prequel that takes place a century ago when humans were forced to live undersea when the cities were Greek named.

Tokyopop licensed the manga series for distribution in North America and published an English language 208-page graphic novel "Daphne in the Brilliant Blue" in 2006.

Carl Kimlinger reviewed Collection 1 awarding grades from "C" (story) to "B" (art & music) giving a "+: for its good sense of humor and a sympathetic lead and "−" for "not-so-good everything else", noting that "a high fan-service tolerance is necessary".

[3] Theron Martin reviewed Collection 2 awarding grades from "C" (animation) to "B" (art & music) giving a "+ as it "can be quite entertaining" and "−" for "stale ideas and distractingly outrageous costume designs".