Since Lucy has only interacted with hateful bullies and traitorous two-faces, it stands to reason she’d have a problem with any other human who suddenly approaches her. But Kouta brings an olive branch in the form of a music box playing a pretty (but sad) tune and an offer of friendship, no strings attached. The appallingly lonely Lucy may not completely trust him, but can’t turn him down either.
For a few blissful days, Lucy gets to spend time with Kouta as an ordinary kid…in between squatting in houses whose occupants she murders. Kouta proves to be a man of his word when it comes to showing up. He thinks her horns are cool, but when he senses she doesn’t feel the same, he offers a hat to hide them on an extended date that starts with a visit to the zoo, where Lucy is delighted by the elephants and giraffes.
The pair end up cooling off in a pond, but Kouta instigates a splash battle that results in both having to strip down so their clothes can dry in the sun. This whole day is the last Lucy will get—Kouta is leaving the next day, after attending a festival with the family he was visiting. She tells Kouta it’s the most fun day she’s ever had, and while he’s sure she’s exaggerating, it’s heartbreaking that she’s not.
At points throughout the date, Lucy hears people chattering about the murders going on, and descends into her head where bandaged “clones” of her feed her negativity. When Lucy fears the cousin Kouta promised to go to the festival with is a girl, those voices intensify, and all of a sudden she’s choking Kouta on the bus. But Kouta is so guileless he shakes it off. The two end up humming the music box song as they watch the sun set, then part ways amicably.
That is, after Kouta tells her that his cousin is a boy, which is a lie. Lucy discovers this because she goes to the festival and spots Kouta with Yuka. A crowd forms around her, watching her, commenting on her, and the voices inside draw closer and become more determined to drive her to the dark side permanently…and she kills all of the people around her.
Kouta doesn’t witness it, but a little girl—perhaps his sister?—did, and described the killer. Lucy glares at Kouta and the girl from a rooftop, betrayed by his lie. A white lie he told to spare her feelings, but a lie all the same. Which makes him just like every other human she’s interacted with.
Back in the present, Lucy comes to, her memory restored. And who should be standing over her but Kouta the liar and his pretty girl cousin. Then we cut back to Mayu and Nana outside the house, where Lucy appears and leaves the premises. It’s ambiguous whether she killed Kouta and Nana inside, though the preview shows them alive and well, so more likely than not she simply left without harming them.
A Lucy this hardened by the years between her encounters with Kouta surely wouldn’t soften her stance on his status as just another liar in her life; someone momentarily interested in an “unusual animal” like her. Her inner voices—and Director Kazukawa—may be right in calling her next level of human evolution, and that her kind is predisposed to wiping out their inferior predecessors.
But what if Lucy is only the way she is because she was always around the wrong humans? If she had had someone kind like Kouta in her life the whole time, maybe things could have been different…