Hiro’s sword is also known as the Armor Breaker. The Armor Breaker belongs to a family of magical swords that empower their users with new abilities at the cost of losing something else. After Zeus, MC, Alfonse, Caesar, and Klaus succeed in making him laugh, he tells the story of how he got the sword in the first place during his freshman year. He says that he was separated from Zeus in the labyrinth that year, and had the courage that he would come looking for him once again. He then decided to take a nap, after a while he heard some calling him and he took the first thing he was able to grab in order to shut them up but instead he found the sword. The cost was that he was no longer able to use magic. He mentions that he researched and used magic from Hinomoto before obtaining the sword.
It’s mentioned throughout Hiro’s route that he and Zeus have known each other since they were young, and lived together. This is because the Tachibana family once helped one of Zeus’s ancestors many years ago, and since then have served the Brundle family. But Zeus and his father do not view Hiro as a servant but as a relative instead. This is confirmed when Alfonse and Caesar ask them how they met and Zeus says both families lived under the same roof. The MC character notices that Zeus never mentions Hiro's family status and thinks that Hiro might be the only one who is over conscious of this.
During a reunion in the Night Cafe Zeus tells a story that when they were young, he and Hiro were chased by a wolf and at some point Hiro grabbed a branch and put himself in front of Zeus to protect him. Zeus laughs remembering how little Hiro was shaking so badly that he thought he was going to fall at any moment. Even though Hiro is embarrassed about this anecdote he has fun with the Prefect Group.
During a visit to the Headmaster's office, Rembrandts announces Hiro that he was postulated by Zeus to take the Prefect trial to become a new Prefect of the Night Class, which the Headmaster approves and encourages it. However Hiro rejects the offer and leave the office leaving the rest disappointed. They all go to the Night Cafe and try to convince to take the trial and only after talking to Liz Hiro says he might consider it. Though it's a great advance, he's still not fully convinced.
To make him change his mind, Zeus summons a creature so Hiro can get rid of it and thus proving he can handle difficult things and become a prefect. Despite his intentions, Hiro is still reluctant to take the trials and he tells Zeus he knows the reason behind his rejection. Zeus then figures that it has to do with the sword and explains the rest of the group that Hiro can't use magic. When they go again to the Headmaster's office (Zeus had been told off due to the incident of the previous day), Rembrandt assures Hiro there was no rule that said a Prefect must be able to cast magic. The group finds out that the Headmaster was the only one who knew how Hiro got his sword and they all get curious on how he acquired it since not even Zeus, his long-life friend, didn't know the story and Hiro didn't want to share it. Hiro makes a bet with the group with the only instruction that if they made him laugh, then he would tell them the story.
Excited about the challenge, they all accept the terms and next day each prepare a thing that could make Hiro laugh but an eventful of combined accidents was the thing that made the trick. After Hiro laughs out loud on Zeus and Caesar's expense, he fulfills his bargain of the deal. This is what also does the trick to convince him he can be a prefect even with his flaws. He accepts to become a prefect candidate on the sole condition that Liz judges his trials, which the Headmasters accepts. The first trial goes well and Hiro passes, but at the end of the day they find out Caesar is missing. They all go looking for him the next day, and find out a lead to a girl in Liz's dorms.
At first the girl doesn't want to cooperate with them, but then they find out that prior to the events of the route, the girl had confessed her feelings to Hiro and asked him to be her boyfriend and Hiro had rejected her. Because the girl was still holding information that could have had a lead on Caesar's whereabouts, Hiro dismissively tells her he couldn't care less about her confessing to Caesar too since he didn't like her at all. Liz reprimands him and tells the girl she wouldn't get into trouble and makes her understand they were just worried about Caesar. It turned out that after confessing to Caesar, the girl kissed him on the cheek and he disappeared. They eventually find Caesar and even Hiro gets a little jealous when Pig Caesar cuddles in Liz's arms. During the reunion Liz approaches Hiro and asks him about not being sympathetic towards the girl's feelings. Hiro responds that if he's not interested in someone he just doesn't care. In order to get him understand people's (especially girl's) feelings Liz pretends to tell Hiro she doesn't care about him. When Liz was about to tell those cruel Hiro stops her and get her point and assures her he will be more considerate in the future.
In his second trial, the Headmaster announces Hiro that he had to defeat a fierga, which is a creature that feeds from people's fears. Hiro dismisses this task as an easy one believing he wasn't scared of anything. As a precaution, Rembrandt asks the other prefects to watch the trial and to interfere if things get out of control sensing the fierga as an unstable creature. Hiro seemed to have deep fears which led to a catastrophic event: Trying to protect Hiro, Zeus launches in front of him and is attacked by the fierga and this put Zeus in a coma. Feeling guilty due to his lack of self control on his fears, Hiro rarely sleeps and is rude to practically everyone until Liz makes him understand that everyone is worried not only about Zeus but as well as Hiro. During this time, Liz confesses to Hiro and they start their relationship. The Headmaster and Alfonse discover a potion that could wake Zeus, but there were some ingredients difficult to find. The main one was a plant that only grew in a specific far away country. When Hiro tells them the plant also grows in a part of the labyrinth, they all set to find it. During the trip they all discover that Hiro and Liz are dating, which makes everyone happy. They all head to the Lake of Insanity, which is a haunted place and, after fighting Hiro's fierga again, they collect the plant and return to the Academy. However during the battle with the fierga, Liz senses that something is wrong with Hiro although she can't put her finger on it. After they return, Alfonse makes the potion an Zeus wakes up, which makes everyone glad.
Zeus learns about the new relationship between Liz and Hiro and chases after them through all the Academy until they reach the Labyrinth and since Zeus was so persistent on seeing them kiss, Hiro gives him the show he wanted, much to Lucious' dismay who seems happy about Liz but a little nostalgic of his relationship with Claudia. After that they all go to the Night Cafe to celebrate Zeus' recovery and there Zeus learns that Hiro went to the labyrinth's forest for him, which reassures Zeus Hiro's loyalty and care for him, since Hiro had avoided that place since it was where he had gotten the sword. He then tells them a story of Hiro protecting him since they were kids. Though Hiro is embarrassed of Zeus telling those kind of stories he's still glad he can enjoy spending time with Zeus and the other prefects. It's also noted in this reunion that the results of Hiro's second trial remained unclear due to Zeus' condition.
After having fun on Alfonse's expense they all go back to the labyrinth where Zeus teasingly starts to tell other childhood story, although Hiro tries to stop him threatening to slice him. However, Zeus uses his magic to freeze and shush Hiro. When Hiro walks with Liz, she tries to tell him how Zeus seemed to show off his relationship with him as brother might do. Liz speaks so well of Zeus that makes Hiro jealous, and they promise each other to never have eyes on anyone but between them.
The next day Liz receives a magic note telling her she had to hurry to the Headmaster's office where Rembrandt says to the group that it's occurred another incident in the Underground Graveyard. Klaus is asked to help since it could have something to do with the BBW case. When they talk with the headmaster and Lucious, they discover that BBW stands for Big Bad Wolf, the former wielder of the Armor Breaker and they sense that his soul is in the sword and also they fear that the next target is Zeus. They all go looking for Hiro and find him in the lake near the underground castle. Liz senses something's wrong and Hiro says his good-bye to her. Zeus then confronts Hiro for not coming to them and asked for help and Hiro replies that they were not his friends, but Liz can tell that he didn't mean those words. Hiro reveals he has gradually becoming BBW's puppet.
Big Bad Wolf reveals himself and takes full possession of Hiro's body and he reveals that what he wanted from the beginning was Zeus' body. After a combat in which Klaus, Caesar and Alfonse help Liz and Zeus they manage for Hiro to let go of the Armor Breaker and this causes BBW not being in control of Hiro anymore. However he still wants Zeus and goes after him. The other attack again and Hiro is able to cast magic again since he got rid of the blade. Using Hinomoto's magic spells Hiro casts a hell's fire and this destroys BBW's essence.
When they return to the Night Prefects' office. Hiro reveals he had know about BBW since he got the sword. He explains that after he got the Armor Breaker in the Lake of Insanity he felt that BBW could become more powerful every time he got nearer that place or the labyrinth. He also revealed that Hiro was made to put the message on the wall and the attack that opened the BBW case. Zeus asks why he didn't come clean as soon as he got the sword and Hiro responds that it was because he had to deal it on his own. Zeus and Liz comprehend that Hiro felt that way because of his "duty" to protect Zeus, which enrages him and makes Hiro apologize over and over. Then, Zeus lets Hiro know that despite the relationship their parents have, theirs is different, therefore Zeus makes Hiro understand they're not master and servant but equals, which makes Hiro happy and shy. Zeus and the others tell Hiro that his punishment will be to clean the Night Prefects' office and to make it spotless. Hiro and Liz stay behind "to clean" but they renew their love for each other when they are left alone.
Normal Ending.- After telling the Headmaster what happened in the labyrinth, Hiro is punished for being the cause of all and he is appointed to clean all the Academy's walls. The headmaster also announces that Hiro is now a new Night Class Prefect and therefore he hopes that he carries his punishment with responsibility as well as remorse for his mistakes. Hiro is surprised to hear he was made Prefect, but the Headmaster says he changed the second trial for what happened at the Lake of Insanity and the third trial for closing the BBW case. Though Zeus is happy to hear his best friend is a Prefect now, he has an argument with the Headmaster saying that the punishment was way too strict and difficult for Hiro, since the Academy was very large. Headmaster then appoints the rest of the Prefects to help Hiro and has Klaus to supervise them. They get upset and joke that they will get Zeus later, which scares him specially because Alfonse threatened him with an evil smile. Later, while they're cleaning, Hiro kisses Liz which causes Zeus to make a little tantrum of how they are having their own fun and demands Hiro to apologize again and thank the rest of the Prefects for their support and their friendship. Afterwards they decide to go the Night Cafe to have a relaxing moment. Klaus joins them and Hiro with Liz stay a little behind talking to each other and vowing to be together.
Meanwhile in the labyrinth it's shown that BBW barely survived and is intercepted by Strange Taffy, who had hoped that BBW and him had the same goal. However when finding out they differ in what they wanted Strange Taffy gets rid of BBW and says he has to inform his master of this.
On the outside Hiro seems to be an expressionless person, but deep inside he cares for his friend even if he doesn't show it, especially for Zeus and the MC character (in other routes he cares for her as a friend).
In his route he displays a more open personality laughing and smiling more. Though he's still a little embarrassed to show his emotions and he even tells Lucious how he's a little jealous of him since the prince can't hide his feelings thus people are able to know how to respond to him.
In his route Hiro can be a little jealous toward the MC character, since there was a time when Caesar as a pig uses his cuteness and size to cuddle in Liz arms, he took Caesar of his neck and reminded Liz who the pig really was. And also when Liz tried to teach him to be sympathetic towards people's feelings by telling him she didn't care about him, Hiro felt really bad and stops her before she could pronounce those words.
Also in his route he's less shy when he finds out he loves Liz. He declares to her openly and asks her to be his girlfriend. And when Zeus was so obsessed to see them kiss, he does it without hesitation and there are other times when he likes to show his relationship not caring who is around which causes a bit of distress to Liz who is shy and conscious of the people around her.
Hiro also has a love for muffins and gets in a bad mood when Zeus ate his muffin he was saving for breakfast. He appreciates Liz baking muffins for him since she offered to bake some more muffins. In his Happy Ending, he even turns violent and threatened those who tried to take it from him, even though Liz baked enough muffins for everyone so they won't go starting a fight.
- In "The Trust" spin-off Zeus mentions that Hiro used to hate his guts until there was an incident with a woman.
- As Hiro had been together with Zeus since birth, Hiro's hometown is also Queensblade Kingdom.