Kokoro

Kokoro (ココロ) is one of the main characters in DARLING in the FRANXX series. She's a Parasite with codename "556" of Thirteenth Plantation, where she's partnered in boy-girl pair with Futoshi to pilot a FRANXX called Genista.

Appearance
A beautiful girl with long, wavy, ashen blonde hair and rich blue eyes. She wears a lacy blue headband to keep her hair out of her face.

Personality
A very gentle soul with a kind personality to match. She doesn't speak too often, but when she does her words are well thought-out and meaningful. Her FRANXX partner is Futoshi.

History
Like the others, she was raised in the Garden with the other parasites and went through the same amount of training.

Futoshi
She gets along exceedingly well with her partner, comforting and complimenting him. During their first time in Genista they flash each other a thumbs up in the cockpit before beginning, and Kokoro reassures him he did a good job as they take their first steps.

They seem to have, as Zorome describes, a "lovey-dovey" relationship. In the second breakfast scene Kokoro offers Futoshi the seat next to her when Zero Two takes his spot, and she later hand-feeds him toast.

Miku
Miku tends to talk with her the most, with their dynamic being with Miku being the energetic of the two while Kokoro is the soft spoken.

Mitsuru
Kokoro and Mitsuru have random walk-ins with one another mainly inside the greenhouse which Kokoro frequents inside while taking care of the plants.
 * In episode 5, Kokoro sees Mitsuru enter the garden greenhouse and follows him inside. She witnesses Mitsuru taking pills, possibly for the pain, and she offers him help, but he refuses it and sees it as Kokoro is pitying him.
 * In episode 7, while discovering an old town nearby the beach, he reassured the parasites that he could not guarantee their safety so it was there choice whether to come or not. He was mostly telling Kokoro, that he wasn't forcing her to come. While they were looking around, and Kokoro wandered off her own and the others noticed she was gone. Mitsuru was the one who found her and saved her from possibly being injured from falling debris. Kokoro had found a book on babies, and taking care of them. He reminds her not to go off on her own, which she apologizes to doing so.
 * In episode 8, Kokoro goes inside the greenhouse to water the plants, and once again runs into Mitsuru inside. She asks him if he has an interest in plants, and he explains that the greenhouse is the only place he can be fully alone. She starts naming flowers and explains to him what a few of them mean in the flower of languages. She asks him if he is okay with chatting with her, because the boys and girls were going through a gender fight in the episode and refused to be seen with the opposite sex. Mitsuru comments that the fight is stupid and immature, and he isn't doing it, to which Kokoro praises him for being able to say what he thinks, because she finds it hard to do so. As Mitsuru was leaving, Kokoro stood up to suddenly, and the book on babies fell out of her pocket. Mitsuru asks if she brought it back. She didn't say anything and just held it to herself as he walked out of the greenhouse.

Etymology
Kokoro's nickname may use some of the numeral's readings from her real name "Code:556": ko, an alternative spelling of "5" and ro as in 6.

Kokoro is also the japanese word for "heart"