Yuzuru was born into the life of a butler. Even at a young age, Yuzuru was tasked as a servant, with the intent of making him Tori's lifelong personal servant. He practiced housework and courtesy among other things, and was able to pick up these skills even as a child. However, according to Tori, Yuzuru did often make careless mistakes when he was younger, and "he was often scolded and secretly cried in the shadows". It is unknown whether or not he received any formal schooling at this age, but since Tori has had personal tutors at the residence, it is possible that Yuzuru received schooling in that way as well. These mistakes might be part of the reason why Yuzuru was sent away to a Himemiya-owned military training camp during his childhood. At the camp, he was expected to train so that he could protect Tori from any potential hardship. This included possible abduction and assassination attempts, and so his training was very rigorous. While at the military camp, Yuzuru met Ibara. Due to being the only two boys of similar age in that facility, they end up forming quite an odd relationship with each other. Ibara implied to often tried to kill Yuzuru on multiple occasions as his attempt to overcome Yuzuru's skill. Yuzuru seemed to be bothered by that attitude because Yuzuru always wanted them to get along but Ibara knew Yuzuru will eventually leave so he preferred to avoid getting too close to Yuzuru. Nevertheless, Yuzuru still did his best to be kind to Ibara, he often cooked proper food for him and even made dessert only for him, in which it became the rare good memory for Ibara to remember. However, they later had a falling out due to Yuzuru returning back to being a butler for Tori. Over the course of this training, Yuzuru gradually became more and more resentful of his parents and his situation in life. By the time he was allowed to return to the Himemiyas, he felt that it would be better to "face the battlefield and dissolve like the morning dew, than to spend [his] entire life as a millionaire's pet dog." He thought that death would have been favorable, just to make his parents feel miserable for what they had done. Even though he had these feelings, he still—albeit reluctantly—came back to his station. Upon his return, he was lovingly embraced by a sobbing Tori, telling him how lonely he was by himself. At that moment, Yuzuru found his warmth, and had a reason to live on as a butler. It is unknown exactly at what age Yuzuru was finished with his training. We do know that Ibara left the military camp at the beginning of middle school, so Yuzuru was likely around 12-13 when he returned. Yuzuru was not present at Yumenosaki for his first year of high school, and as such did not take part in the war. However, he did attend fine's live shows regularly during this time, as Tori was a huge fan of Eichi's. He and Tori were both in the audience for fine's final showdown against Wataru. Eichi notes that his appearance is quite contrastive to that of Tori's—Yuzuru still had his long hair, wore punkish clothes, and looked like a "street fighter". Eichi also comments that he was unaware of Yuzuru's relationship with Tori, beyond Yuzuru being Tori's "young guardian" at this time. At some point during this year, Tori decided to become an idol because of Eichi. Therefore, as Tori's personal servant, Yuzuru had to follow him. Yuzuru cuts his hair and cleans up his appearance before entering Yumenosaki as a second year transfer student.
Yuzuru has a calm and polite demeanor. He is skilled at taking care of others, and genuinely enjoys activities like housework that others would find bothersome. Since he is used to following orders, he is still learning who he truly is and what he wants. Overall, he has a caring personality, and appears to have had one since a young age. He can get restless when he is not allowed to help others. He enjoys cooking healthy meals for the people he cares about, and has recently picked up gardening to keep himself busy. While he appears to enjoy drawing, he has no genuine artistic talent – even his most innocent drawings tend to be misunderstood as demons or monsters. Midori, who has a love for ugly-cute things, is a big fan of his pieces. He has a phobia of dogs, which makes taking care of the Himemiya family’s dog, King, quite troublesome. He apparently used to be a crybaby, and he still tears up easily whenever Tori is successful or expresses affection towards him. According to Wataru, Yuzuru’s interest in keeping things tidy and clean may be a way for him to feel in control, a hint to a more arrogant personality beneath the surface. Yuzuru appears to confirm this hypothesis. He is protective of Tori and Tori’s younger sister, as well as his juniors. This can sometimes make him overbearing – for example, he goes as far as personally censoring Tori’s manga. Hints towards his military past can sometimes seep through in his everyday behavior, causing some characters to be intimidated by the reactions he has in tense situations, or by the uncharacteristic bloodlust-like excitement he displays in times of danger or conflict. Yuzuru’s polite and detached way of speaking is a result of his upbringing as a butler, and he finds this way of speaking easier compared to casual speech, since he got used to it at a young age. He's mentioned that a servant's demeanor has been drilled into his head since a young age, and as a result, he does not know how to enjoy himself the way other people his age do during his free time. He often finds himself completely disoriented about what to do when he's not taking care of Tori. Due to his profession, Yuzuru tends to put a certain distance between himself and others, and seems to be afraid of closing said distance. His attachment to Tori and his worrywart tendencies used to get in the way of his social life; however, he has since begun expressing more vulnerability around others and making friends outside of Tori, as well as building a more genuine and balanced friendship with Tori himself. When particularly emotional, especially around Tori, he can regress to a sort of “baby talk” and refer to himself in third person. His formal speech often hides snarky, flippant remarks, especially around people he finds unpleasant or annoying, or people he is close to.
