Sand Castles ( 砂上の楼閣 / さじょうのろうかく / sajou no roukaku / A Castle In The Air ) is the fifty-fourth chapter of the Elfen Lied manga series.
Nana wakes up from a nightmare about multiple Yen Notes attacking her, for which she blames Mayu, who offers to cook her up some rice for a midday meal since she overslept. Nana is overwhelmed by how delicious her meal is, having never tasted properly prepared food before, while Kouta feels a bit hungry due to the meal being spread out so thinly for the extra guests. Yuka pokes fun at him and then suggests they take a walk in Enoshima Park. Nana at first rejects her suggestion that she change her clothes, owing to her torn dress, but Nozomi offers to sew up the sleeve while Nana and Mayu take a bath. Kouta is seemingly reluctant to agree about Nana staying and is tasked by Yuka for it.
In the bath, Mayu tells Nana that Kouta is likely holding a grudge against her for the attack on Nyu, but Nana luxuriates in the onsen, and remarks to herself on a cleansing markedly different from the harsh ones she got at the Diclonius Research Institute. The evening is capped off by her first taste of ice cream, which she loves so much, she also gets her first brain freeze. Nana is thrown by how different this life is to one of pain and suffering, a life of possible happiness, but for her stubbornness and Kouta's seeming pronouncement. Kouta then reveals that he was playing a bit of a wordplay game with Nana and that in fact, she can stay, so long as she aids in the house cleaning, a trick for which Yuka rides him, but he defends this by citing her obstinacy. Nana cries tears of joy at having a real home, apologizes for being stubborn, and realizes that she doesn't need to be afraid or alone anymore.
On the beach at Kamakura, Nana encounters Bando, to whom she denies having found Lucy, not wanting to destroy her new happiness. At that same moment, Nana senses another Diclonius in a helicopter passing overhead, containing Isobe and Mariko, who asks if she can kill the one she senses below since she apparently has orders not to kill Lucy.
- With this chapter, Nana, the last main character to meet the others, finally begins to reside at the Maple House. We also see a happy meal with the entire group that precedes a major battle, a recurring theme in the series.
- On this chapter's cover, we see that Mayu and little Wanta are never far apart, even apparently in the house's onsen.