HiroMitsu

HiroMitsu is the slash ship between Hiro and Mitsuru from the Darling in the FRANXX fandom.

Canon
Hiro and Mitsuru have known each other since they were small children living in the Garden. When Hiro began naming all the children, Mitsuru shyly asked if Hiro could give him a name, which Hiro did. Following this, Mitsuru idolized Hiro and often followed him around, admiring him for being a genius. When they were 9-years-old, Mitsuru decided to risk his life and get an Elixir Injection to increase his aptitude results. However, before going to get the injection, he told Hiro that he wanted to become a parasite and fight along side him, and if he came back alive, he wanted to pilot a FRANXX with Hiro. Hiro agreed and they pinky promised. Following the procedure, Mitsuru survived and went to see Hiro, who, unbeknownst to Mitsuru, had his memories altered due to running away with Zero Two. Hiro has no recollection of the promise, devastating Mitsuru and shattering his faith in others. Since then, Mitsuru has been determined to surpass Hiro in everything, especially piloting a FRANXX.

When they are 14, they are assigned to the same FRANXX squad. While Mitsuru passes his capacity test with Ikuno, Hiro fails with Naomi and is obligated to return to the Garden but, because of his status as a special specimen, he is offered to stay. Mitsuru doesn’t care what hiro chooses to do but instead sarcastically asks everyone to consider Hiro’s feelings on failing. Following the j code to in which Hiro, while unconscious, piloted Strelizia with Zero Two to neutralize a klaxosaur during the startup ritual, Mitsuru didn’t believe it and said Zero Two is capable of piloting a FRANXX on her own.

During the squad’s first mission, Mitsuru offers to pilot with Zero Two to save everyone from bei gnkilled by a horde of klaxosaurs after Hiro is refused to pilot with her. Zero Two refuses but Hiro reluctantly tells her to go with Mitsuru. While leaving, Mitsuru tells Hiro he will prove he is a better pilot than him. Hiro feels uncomfortable seeing Zero Two go with Mitsuru, as he really wanted to pilot with her. During the battle, Mitsuru becomes empowered by the experience and parades how he can be a better partner to Zero Two than Hiro, which troubles Hiro. At the end, Hiro notices that Mitsuru doesn’t come out of the cockpit, as he is severally injured and traumatized. While recovering, he warns Hiro not to pilot wth her again or else she will kill him. This makes Hiro feel torn on what to do.

After Hiro rides a second time with Zero Two with no issue, Mitsuru reacts with jealousy as everyone praises him and he goes to the greenhouse to sulk, where he is found by Kokoro. During Hiro’s third ride, he almost succumbs to the effects but miraculously survives. Upon seeing Hiro emerge with Zero Two from the cockpit, Mitsuru and the others go to congratulate him, though Mitsuru doesn’t speak to him.

While on a vacation to the beach, Mitsuru tells Ikuno how Hiro is smiling now whereas he was acting depressed and suicidal recently. Later that night, after exploring an abandoned modern city, Hiro wonders why humanity abandoned the surface for the plantations. Mitsuru defends Papa, saying it was to protect humanity from the klaxosaurs.

Shortly after, Mitsuru has a dream from his childhood, telling his child self not to look at Hiro with admiration before waking up and reminding himself why he stopping trusting others. Upon falling ill and being hospitalized, Mitsuru continues having a dream of his child self following Hiro around and about the promise. Due to his incompatibility with Ikuno, Nana proposes the squad try a partner shuffle. Ikuno deduces Mitsuru really wants to be acknowledged not just by Papa and the others but by Hiro, and he tells her to be quiet. After being paired with Kokoro, which devastates Futoshi, Hiro asks Mitsuru to understand but he retorts Hiro is in no position to tell him that.

Later that day, while in a battle, Mitsuru shuts Genista down out of despair for not killing the klaxosaur and Kokoro gets him to confess that Hiro breaking their promise is what made him unable to trust others. After they talk it out and return to the fight, Mitsuru tells himself that he doesn’t know if he can forgive Hiro but is willing to be more civil.

During a trip to the Garden to undergo testing, Hiro is surprised to learn Mitsuru went to the lab once before, which irritates Mitsuru. A couple of days later, after Hiro is hospitalized when Zero Two tried to kill him in a moment of rage, Mitsuru is in his room with the others. As they all start to leave, Hiro calls out to Mitsuru and brings up the promise, now that he has regained his memories. Mitsuru is surprised but then says he forgot about it a long time ago, implying Mitsuru is aware why Hiro forgot about it and he is willing to let it go. Mitsuru tells Hiro not to go near Zero Two again before leaving. However, as Ichigo tries to ban Zero Two from seeing Hiro, Mitsuru and the others grow tired of it and convince Ichigo to let the two meet anyway, which goes horribly wrong.

For the siege of Gran Crevasse, Hiro is grounded while the others go into battle. His friends vow to protect him. Hiro thanks them and all of them, including Mitsuru, smile.

A month later, Mitsuru and Hiro inspect he water in a lake, which they notice is foul and start to wonder wats to filter the water. Mitsuru later talks to Kokoro, who gives him a haircut, about how his grudge against a Hiro was uncalled for since Hiro did nothing wrong. He now believes he used the grudge to give himself a drive and, without it, he has nothing. When Hiro and Zero Two suggests they all cook their own dinner, Mitsuru quickly agrees but doesn’t say it out right to Hiro, who looks at him in appreciation.

As Mitsuru struggles with his growing feelings for Kokoro and her sudden advances towards him, Hiro finds him standing by the lake and they lay in the water together. Mitsuru says he doesn’t understand and Hiro notes how much he’s changed, due to that Mitsuru has never been so close to another person. Hiro says he wants to get to know Kokoro more and, because Hiro loves Zero Two for that reason, he says that’s what it means to live someone. Mitsuru takes all this in and realizes he is in live with Kokoro. Hiro thinks he confused Mitsuru but he says it’s fine and he is glad they got to talk like this in a long time.

Hiro later tells Mitsuru and Kokoro the meaning of marriage, and they decide to get married themselves before the Squad leaves for the Bird Nest. However, on the day of the wedding, the 9’s and an APE assault team crashes the wedding and takes the two away. This angers Hiro, who realizes parasites are not even entitled to their own happiness and he worries about those two. A couple of weeks later, it is revealed their memories of each other have been altered as punishment. Hiro becomes consumed with anger towards Papa for doing this and it provokes him to confront Papa, who justifies the memory wipe on the grounds their actions would have jeopardize APE’s objectives. Hiro says him and the squad no longer see him as their papa and he demands they be set free. Papa agrees in exchange for their cooperation in the supposed final battle against the Klaxosaurs, which Hiro accepts.

A few days later, Hiro and the others are shocked when it is revealed Kokoro is pregnant with Mitsuru’s child. While Mitsuru is confused and scared on what to do, he asks Hiro for advice. However, Hiro, lost in concern for a catatonic Zero Two, doesn’t even know what is right and wrong anymore, and can’t give him an answer. The next day, Hiro announces he is going to space to rescue Zero Two despite it being a suicide mission. Mitsuru doesn’t say anything but appears troubled as Hiro explains his reasons, including that he is better off dead if Zero Two can’t smile for him. These words have a big impact on Mitsuru as he contemplates on what to do regarding Kokoro’s pregnancy, leading him to decide he wants Kokoro keep the baby, which he later says has given him a reason to live.

Before Hiro and the squad leave for space, Mitsuru tells Hiro his decision to stay behind with Kokoro. Hiro replies he understands and that Mitsuru wants to reconcile with Kokoro, which Mitsuru confirms. Eight months later, Hiro realizes the baby will be born soon and he wonders what Mitsuru will name his child.

Two years later, while Mitsuru and Kokoro’s daughter, Ai, plays near Zero Two’s statue, she begins saying darling. They realize something is wrong with Hiro and Zero Two, and everyone joins hands to send their prayers to the two in space. Mitsuru says he chose the name ‘Ai’ for his daughter because it means ‘love’, a word he and Kokoro were never taught but learned fromHiro and Zero Two, and they want her to inherit the bond Hiro and Zero Two have. When Hiro and Zero Two sacrifice themselves to destroy the VIRM home planet, Mitsuru mourns the loss of his two friends

Eight years later, Mitsuru and the rest of the squad reunite at a cherry blossom tree to remember Hiro and Zero Two, and all the lessons they learned from those two.

Fanon
The shipping was initially descent among the fans but it began crumbling starting in Episode 15 when Hiro and Zero Two officially confessed their love for each other. It completely diminished following Episode 17, when Mitsuru acknowledged his feelings for Kokoro and consummated their relationship.