She is voiced by Kanae Ito in the Japanese version of the anime, and by Jad Saxton in English version of the anime.
Sena has stated that she inherited most of her looks from her mother. Sena is a very beautiful young girl with a pair of light-blue eyes. She has light-blond hair that reaches her mid-back while it only reaches her upper chest in the front. Her bangs hang just above her eyes. Sena has a very buxom body (Yozora insults Sena because of this, nicknaming her "Meat") and tends to flaunt herself. Sena almost always wears her butterfly hair clip on her head and is usually depicted in her school uniform. When in public, Sena wears flashy clothes that fit her well. In the 6th volume, it is revealed that her butler, Stella, buys her clothes, picks out her outfits, and even does her hair and make-up every day. She is 164 cm tall, making her the second tallest member of the club after Kodaka.
On the outside, Sena appears to be an ordinary high school girl but in truth, Sena is arrogant and prideful by nature and is well aware of this, once even stating that she should do so since she's that good. Sena considers herself to be the school queen or goddess and so often treats her fellow male students as servants, or "doormats" as Sena herself has said (not that they mind). Although because of her personality and beauty, she has no female friends.
Sena also believes that there are two types of girls; the ones who are willing to be her friends and the others who are not worthy of her. Sena also does not treat the boys in her class with much respect due to them constantly ogling her, and slavishly doing whatever she tells them to.
However, whenever Sena's ego is shaken by someone (usually Yozora), she bursts into tears and flings childish insults before running away. Sena was surprised to see that Kodaka does not act like the boys in her class (wanting to be stepped on) and hence, views Kodaka in a different light. She first saw him in this different light when he rescued her from some guys who were harassing her at a public pool. Since then, her feelings have increased to the point where she nonchalantly admits that she wouldn't mind marrying him and that she is in love with him.
A perfectionist by default, Sena always tries her best at everything, and is willing to go to great lengths to do something perfectly (once playing a video game without sleeping until she had finished it). Sena gets so involved in her games that she becomes very angry if they are insulted in any way.
Sena is very gullible, and often fails to see through the tricks Rika and Yozora play on her, even when the resulting humiliation is plain to see, (an example being the "heap" hairstyle). She only realizes her mistake when her father or some other person points it out to her.
Kodaka has noted her obsessive personality; that she becomes extremely engrossed in things she is interested in, sometimes to beyond reasonable levels (as seen with her grudge against Yozora), while completely ignoring things she is not interested in. Since she possesses both the confidence and the means to pursue whatever she may desire, he calls her "a real live princess".
Despite her princess-like arrogance, it's been shown that Sena genuinely cares for the other members of the club. For example, Sena offered to purchase a theme park ticket for Maria so that she would not be left out of the group, which showed a degree of care unexpected from an arrogant princess who thinks nothing of others. Later, while she exacted her revenge on Yozora for plagiarizing, Sena made a point not to go too far and offered Yozora a chance to redeem herself by giving her a part in the movie.
Sena also has an overly creepy obsession regarding Kodaka's younger sister, Kobato, going so far as asking to take a bath with her. Sena will go to any lengths to make Kobato happy, much to Kobato's discomfort.