Hiro

Hiro (ヒロ) is the main protagonist of DARLING in the FRANXX series. He was known as a prodigy Parasite with the codename "016" of Thirteenth Plantation, where he's now officially partnered in a boy-girl pair with Zero Two to pilot a FRANXX called Strelizia in Episode 7.

Apparently 9α referred to Hiro as ' Nine Iota'.

Appearance
Hiro has a standard "slim" male physique with black, shaggy hair and rich blue eyes. His checkered past has left him with an emphatic expression on his face, despite his personality.

In Episode 5, he gains a blue tumor-like mutation in his chest, which was caused by piloting with Zero Two, which increased his yellow blood cell counts, the polar opposite of what happened when Zero Two rode with other parasites. In Episode 6, this mutation grows largely due to piloting with Zero Two again, But later in the Episode is absorbed into his body.

Personality
As a child, Hiro was jovial and hopeful, giving names to other kids and to himself as well, when codes are the only identity and nickname given to them. This earns him fame among other children even those in other squads. He even spent time teaching other children, especially Ichigo, about stars.

A former star student of the academy, Hiro's inability to pilot FRANXX has left his hopes low, even to the point of choosing to leave Cerasus until his former partner Naomi encourages him to stay. His emotions are strong, but his heart keeps him from giving up.

Losing the ability to pilot left him feeling that his life had little worth, to the extent that he is more than willing to ride with Zero Two even if it means his death. However, this wish of his came to an end after he survived his third ride with Zero Two and hence proved the rumour about her being a Partner Killer wrong.

Ever since then Hiro has been thinking about Zero Two and her personal life, in helping her to be stronger and to get closer to her.

History
He came from the same orphanage as Naomi, Ichigo and Goro and later become Naomi's partner. They failed the exam and Naomi was forced to leave Plantation 13. Hiro, however, was given a special permission to stay, which he declined. Naomi's plane was attacked by a klaxosaur, but she survived.

In Episode 6, Hiro faints, and everybody (Including himself) assumes he is dead. He later (Still during the battle) has visions of Naomi & Zero two. He then wakes up, and upon realizing Zero two is incapable of defeating this Guten-berg class Klaxosaur alone, He absorbs the mutation and is restored to good health.

Zero Two
Hiro first met Zero Two when she was skinny dipping. Despite that others may discriminate her for her horns, he found that they are alluring. When they met, both of them were lonely and shared the struggle of not being able to pilot. After kissing Zero Two and piloting Strelizia, he was keen to do it again and prove his ability. Hiro blushes when Zero Two is around him, but does not seem to be uncomfortable with her presence.

Ichigo
Ichigo is Hiro's childhood friend. He cares a lot about her, but seems to be oblivious to her feelings for him. When Hiro piloted Delphinium with her, their compatibility was 100%, higher than any other pair. However, their FRANXX deactivated shortly after. When Ichigo kissed him at the end of episode 2, he felt nothing but guilt.

Goro
Goro and Hiro have a good relationship and grew-up together. He's often supportive of Hiro and cheers him on in his endeavors, hoping that he finds success and happiness. Likewise, he hates seeing him hurt and so learning that Hiro is dying from piloting with Zero Two leaves the latter feeling frustrated. They share a room.

Zorome
Zorome and Hiro have clashing personalities. Zorome often would mock Hiro and his inability to pilot. However, after Hiro pilots Strelizia with Zero Two and saves him alongside the rest of the squad, Hiro makes amends with him, and states that he will try not to be a burden to Zorome and will fight alongside him, which makes him gain respect for Hiro.

Mitsuru
Mitsuru and Hiro have a negative relationship. Mitsuru used to look up to Hiro, but finds his current inability to pilot pathetic. He mocks him and seems to have an inferiority complex against him. He is desperate to prove that he is better than Hiro, stating that he will even become the stamen of Strelizia because he is able to ride it just as good as Hiro. However, he is left greatly injured after riding in Strelizia, which makes him anxiously think about why Hiro can pilot it so well while he can't, showing his great jealousy of Hiro.

Naomi
His former partner while training to become Parasites. When tested in their ability to connect to each other, it is shown that they are unable to do so resulting in failing with Naomi being expelled, and Hiro choosing to leave, despite HQ giving him the rare chance to remain in hopes of getting a partner that is compatible with him. Naomi cares for Hiro enough that she gets upset that he chose to leave Plantation 13 along with her. When they're meant to get on a transport to leave, she prevents him from getting on board by throwing her suitcase at him. The last thing she tells him is that she likes the name he gave her, and that she hopes he finds a good partner.

She supposedly survived the klaxosaur attack and is undergoing medical treatment within Plantation.

She appears again in Episode 6, in the moment when Hiro almost dies, reminding him that his partner (Zero Two) needs him, also that he is lying to himself upon the fact that he is satisfied and that he thinks had done his best.

Dr. FRANXX
Dr. FranXX, Hiro "that boy zero two can fulfill the requests". He said

Papa
Along with APE's council (Known as Lamarck Club, or Seven Sages), Papa refers to Hiro as the "Special Specimen".

Etymology
Hiro's nickname may use some of the numeral's readings from his real name "Code:016": hi from 1 and ro from 6.

Quotes
"I feel myself going deeper inside you!" - Episode 4; he says this to Zero Two inside the Strelizia (of course, not that kind of deep.)

Trivia

 * It is revealed in Episode 3 that Hiro has a chance of being a "special specimen", due to his inability to pilot a FRANXX except for Strelizia with Zero Two.
 * It is said that in Episode 5, the complete opposite happened with Hiro when he piloted Strelizia with Zero Two, His Yellow Blood Cell's Increased instead of decreasing, which seems to be the first time it has happened.
 * Hiro was the one who appointed all the members of the Thirteenth Plantation, which according to Code: 090, is very peculiar.
 * According to Code: 090 and unknown to Hiro, he is famous among children, although at the moment it is not known exactly why.

Hiro Хиро