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.

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"