Kyohei's personality can often be described as confrontational, and often will say whatever is on his mind, regardless of the consequences. It is shown in both the anime and the manga that he is a very good fighter, and is considered to be very dangerous. It is later shown in the manga that he was initially very standoffish to the rest of the boys. Kyohei later warms up to his roommates, accepting them as his friends. It should be noted that unlike his roommates, Kyohei despises the attention that he receives due to his looks.
It should also be noted that while Kyohei is attractive, he often suffers from poor self image. The character frequently drops hints that he despises his appearance, with some hints suggesting that he wishes to become more normal. This is very similar to Sunako, where she too sees her appearance as a problem. However, where Sunako withdrew from society entirely, Kyohei chooses to remain a part of society.
It is shown in throughout the series that Kyohei's good looks were not always a blessing. Unlike his attractive counterparts, Kyohei has not had a good family life. In later volumes of the manga it is revealed that Kyohei had to leave his home to avoid his mother developing a nervous breakdown due to the constant and frightening attention he would receive. Kyohei has also often quit jobs due to sexual harassment from both male and female bosses. In the anime Kyohei is often fired due to overzealous fans destroying the environment around him.
In the story line covering his initial introduction to his male roommates, Kyohei is stalked by hundreds of girls. He initially takes an indifferent stance until Yuki is almost injured attempting to defend him. After this encounter, Kyohei's personality slowly changes to allow only a selected few into his personal life. One such person is Sunako, as she is initially repelled by his appearance, and takes his personality at face value. However, Kyohei's home life came as a surprise to her, as she imagined that not only did he enjoy the attention, but that his family was as beautiful as he was. Sunako was quite surprised to discover that Kyohei's good looks were considered an abnormality, and that his parents and older brother were extremely normal.
In Volume 10 of the US release Kyohei's poor self-image caused him to leave the rental mansion for a short time, believing that his presence was troublesome and unwanted and that if even Sunako couldn't accept him no one would.
While many readers would immediately believe otherwise, Kyohei does not engage in many relationships, personal or otherwise. So far in the manga he has yet to have a (or have previously had) a romantic relationship, despite many characters attempting to force one upon him. Many of his fictional peers believe Kyohei to be dating Sunako, although both characters so far deny any attraction to the other.
Though Kyohei's looks weren't mentioned as the best of the four boys, he is the most popular out of their group simply for the reason that he doesn't have a relationship in some way
n the series Kyohei is very slow to accept friends, since it is shown that many try to take advantage of him in various ways. Gradually, he strengthens his bonds with his roommates and even participates occasionally with the abnormal ways of Sunako. He and Sunako have a complex relationship and it is hazy whether they have romantic feelings for each other. In Chapter 35 to 36, the Landlady, in an effort to make Sunako a lady, tries to force Kyohei and Sunako to sleep together but she accidentally interrupts this. Afterwards, Yuki ask Kyohei whether it was the first time he approached a woman to which Kyohei declines to comment.
At the end of volume 18, Kyohei kisses Sunako on impulse. However, in the beginning of volume 19, Kyohei claims he had a "moment of confusion" because of Noi's previous antics when she was trying to get them together.