The Elfen Lied Special Side Story is a short manga created by Lynn Okamoto as a collectible extra within the Elfen Lied Blu-Ray release. An 8-page long story, it has not been published in any other languages nor included with releases outside of Japan, where it saw release in 2012, the tenth anniversary of the manga series. It is apparently set not in the manga continuity, but rather, in the anime's, and its timeframe seems to be around that of the OVA episode, perhaps occurring some time after that.
On a hot August day, the residents of Maple House are suffering through a heat wave, especially Nana. The small fan is not working, and Nyu is hanging out the side door to get some fresh air from outside.
The idea arises to go the beach, which despite being crowded, enchants them all, most of all Nana and Nyu (Oddly, the two Diclonii wear no hair ribbons or caps so their horns in plain public view; something not explained in-story). The girls are in bikini bathing suits, and Kouta is wearing swim trunks.
Nyu immediately makes for the waves in an inner tube, while Nana spots their sometime-nemesis Bando, though he does not spot the two Diclonius girls. He's more concerned with beach-goers throwing trash onto the beach, which he scoops up while scolding them.
Kouta and Yuka talk quietly sitting on the beach blanket. The music box is also with them, issuing a caption indicating silence, while dialogue from offscreen regarding Nozomi, with one speaker, presumably Yuka, thinking Nozomi would enjoy the day, and the other, most likely Kouta, having no idea who Nozomi is.
Not far away, Nana coaxes a reluctant, fearful Mayu into the water, while Mayu would rather sit and cuddle with Wanta. Once in, her splashing about confirms that Mayu cannot swim, and Nana laughs at her inability to swim as well as her discomfort. Thankfully, Mayu is only in danger of embarrassment.
Realizing that a fireworks display is scheduled for that evening, the group changes from swimwear to regular clothes. Kouta and Nyu stare in abject wonder at the display. Yuka is slightly thrown by Kouta's wonder but makes no comment on it. Nana is overwhelmed by the noise and lights of the fireworks, hiding beneath a table, thinking that they are under some enemy's attack. Mayu engages in a little playful payback for the earlier teasing she endured in the water. The piece ends with them all watching the fireworks, with Nana staying under the table.
- Nana's upbringing is brought up by inference: raised in a laboratory environment, she is not used to the extremes of hot weather, nor has she ever seen explosives used for entertainment purposes.
- The presence of the music box firmly places this piece in the anime continuity, but Nozomi, noted for her absence from the anime, is mentioned in passing by Kouta and Yuka. Since the music box is a sort of 'stand-in' for Nozomi, it seems to be an in-joke.
- This vignette is the first story set in the anime continuity since the release of the OVA in 2005.
- Mayu's inability to swim raises concerns about what she was doing when she first met Wanta on the beach. Combined with her placing her shoes by the shore in an orderly fashion (in Japanese culture, those committing suicide remove their shoes beforehand and place them close together), it's highly possible she planned to commit suicide before Wanta intervened.
- Despite it being a central location for many events in both versions of the series, it seems, based on dialogue, that the beach shown here is not, in fact, Yuigahama Beach. It is Katase Beach where the Enoshima Oohashi Bridge is located. On the western side of the bridge, they set off fireworks. They swam on the eastern side of the beach given the manga scenes. The fireworks display was always held on the first Tuesday of August until 2009 (from 2010 on it is changed and now held in October). So this exclusive side story portrays an ordinary and peaceful day that the Maple House family could have in early August. More specifically it must be August 6th if it was in 2002, or August 5th if it was in 2003, depending on the timeline of Elfen Lied series.