Those time passages...

Previously In Timeline

Year Event(s)
17 ALB Around the world, Diclonius children were born from the virus unleashed by Chief Kakuzawa. Those who were not euthanized at birth began to exhibit vectors and turned against non-horned humans. Any attempts to contain, treat or keep them from using their powers to kill were not recorded in the series.
17-20 ALB The Diclonius War begins, exacting a heavy toll of losses among the human population, and necessitating a birth ban until a vaccine developed by Arakawa can be used to prevent further Diclonius births. According to an account by Kouta, humankind is teetering on the brink of extinction during this period. It seems that, wherever they all live at this point, the residents of the Maple House keep in contact with one another.
20-23 ALB Kouta gets married, presumably to Yuka, and they have a daughter, whom they name Nyuu in honor of their late friend.
18-28 ALB Kouta keeps his promise to Lucy/Nyu and returns each year to the spot they first met on the last day of the Kamakura summer festival.
28 ALB On the last day of the summer festival, Kouta brings his young daughter, little Nyuu, to the spot and tells her the story of his friend. Nyuu finds a jar containing a note and a keepsake from the original Nyu buried where Nyu laid her puppy to rest. Lucy\Nyu's real name is revealed to be Kaede, and little Nyuu tells Kouta that she has been playing in those same mountains with a pair of twin girls. They appear, and Nyuu calls one of them Kaede. The girls tell Kouta that they have been waiting to meet their special friend. They are apparently reincarnations of Lucy and Nyu, but the series does not make this entirely clear.

See Also : The Diclonius War \\ Anime Timeline