Yuu Yanase (柳瀬 優, Yanase Yuu) is a supporting character in the Sekai-ichi Hatsukoi series. He is in love with his close friend Chiaki Yoshino.
Yuu has medium-length brown hair and light maroon eyes. He is also seen to wear glasses when he's working in the manga and often favors a light brown duster jacket when working with Chiaki.
Yuu has known Hatori since junior high school. From the start, the two did not have a very good relationship and appeared to strongly dislike one another, though the reason why is initially unclear. It is speculated that their trouble with each other stated a result of their mutual desire to get close to Chiaki and have a rivalry to do so.
Every time they meet, there is obvious tension between them, resulting in barbed insults and double-edged compliments. The main reason why they never get along is soon revealed to be because they are both in love with Chiaki and wished to have him as their own. However, even though Hatori dislikes Yuu, he respects his skills as a mangaka's assistant and will not hesitate to ask him for help in matters regarding Chiaki. Likewise, Yuu has been known to call Hatori when worried about Chiaki, letting Hatori know when something seems to be wrong.
Yuu and Chiaki have been friends since junior high when bonding over their interest in books. Also, Yuu admitted how when he saw Chiaki's hands, he thought they were "perfect" upon first sight, which cemented his instant crush on him. It is known that Yuu has a crush on Chiaki, though Chiaki is oblivious to his feelings and only considers him a good friend.
Though they are the best of friends, they also quarrel quite often, mostly over Yuu often making romantic or sexual advances on Chiaki. Despite these attempts, for a long time, Chiaki was unaware of how Yuu felt towards him, finding out only after Yuu had become drunk during their spa trip around Chiaki's birthday. Between the two, Chiaki has always relied on Yuu, stating that the latter is always doing things right.
They have significant trouble when Yuu snaps and attempts to force himself onto Chiaki when alone in his home. He suggests that Chiaki can fall in love with him if he has sex with him and again attempting to kiss and touch him. Chiaki, refusing, ends up punching him to get him off. Yuu then begins to cry, demanding why Hatori is Chiaki's only exception in such an area. Chiaki begins to say he simply doesn't know, to which Yuu remarks that he very does know why. After Chiaki leaves with a furious Hatori, who came to get him, Yuu then reels from being heartbroken. Despite this, the two continue to remain good friends.
- Yuu dislikes sweet foods.
- Like Chiaki, Yuu is a fan of the "Za Kan" manga series by Ijuuin Kyo (from Junjou Romantica).
- Yuu is also a manga assistant of Ijuuin Kyo.
- He is the only male assistant to be seen working with Chiaki.
- Yuu/Chiaki is referred to as "Rejectica" due to the nature of Chiaki's feelings towards Yuu and that he doesn't feel the same about Yuu as he does him.
- Yuu has stated that he became a mangaka simply to be close to Chiaki. This is similar to Hatori becoming a manga editor, as he did it also to stay close to Chiaki.
- Though a major failed love interest in the series, very little is known about Yuu's personal life.
- Yuu appeared in Junjou Romantica manga, a chapter from Ijuuin Kyo's POV. On the day Misaki ultimately rejected Ijuuin, Yuu dropped by at Ijuuin's studio to assist him with work. Ijuuin expressed his gratitude for helping him on short notice and regret that he couldn't give Yuu any day off. He mused that a lot of assistants quit after a short period but Yuu lasted longer than other assistants.