Yuuji was once a sweet innocent little boy who Kazuki Arisaka was in love with. He was somewhat lecherous when he was little, but Kazuki doesn't remember. That is until he left for 10 years only to come back as a naughty girl-chaser. He is constantly finding himself in situations where Kazuki is half-dressed, constantly has lewd fantasies, and sometimes ends up touching girls where he shouldn't be touching them. Despite this, it seems that he does have a nice, kind side, and actually values Kazuki's friendship; this being shown when he was helping her pick out a swimsuit, even though they might have been more revealing with each choice he was picking them as they were her favorite color. Throughout the story it is suggested that he is in love with Kazuki (though he might be unaware of it) as he appears to direct all of his perverted actions to her.

(Source: Wikipedia)