| 柏崎 星奈|
|Date of Birth||May 19th|
|Job||High School Student|
|Class|| 2-3 (Formerly)|
|School||St. Chronica's Academy|
|Japanese Voice||Kanae Ito (Japanese)|
|English Voice||Jad Saxton (English)|
|Novel Debut||Chapter 2|
|Manga Debut||Chapter 2|
|Anime Debut||Episode 1|
Neighbor's Club membersEdit
Sena seems to have a strong dislike for Yozora since the moment she first met her, calling Yozora "weasel" or "flat chest" (although Yozora was the one who treated her harshly first). Most of the time, Yozora would win any arguments she has with Sena, causing the latter to run away, in tears, flinging childish insults.
However, it was shown that Yozora and Sena may be progressing into more of a frenemy territory. For instance, Sena actually seems to like her humiliating nickname "Meat", as it's the first nickname she has ever been given. When Sena was really hurt by Yozora, Yozora was actually rather worried and was even relieved when Sena was no longer angry. As love rivals, Sena tends to get jealous when she notices how casually Kodaka is having chat with Yozora, and when their mutual past was finally revealed Sena was quite shocked and somehow saddened by this fact.
Sena grew an unhealthy fixation towards Yozora that can be interpreted as some sort of fetish, as shown when she has numerous voyeur shots of Yozora posted on the ceiling of her room whilst having in her possession the blonde wig she wore at one point. She claimed to have used these to revitalize her vengeance towards Yozora as it reminded her of all the shameful things she had done to her.
Even though being in a frenemy-like territory, Sena seems to care more for Yozora than the latter does to her, despite the fact being bullied by Yozora quite often. As it was shown when Sena remarked that her childhood friendship with Kodaka was ancient history, causing Yozora to become enraged at Sena and saying that she wished that Sena never existed. But Sena, though admitting that she loathed Yozora with all her soul, said that she never once thought of wishing the same thing to the latter.
Their friendship would later be officially established when Yozora risked herself to protect Sena when she was being confronted by a group of girls. Though Yozora's efforts went unto deaf ears forcing Kodaka to take the brunt of the hurt in their stead , Sena was nonetheless genuinely grateful for Yozora. Furthermore, even before the fiasco in their Christmas party, Sena had already planned on giving Yozora a birthday present, which speaks volumes regarding her friendlier outlook towards Yozora. Finally, Sena viewed Yozora as special, despite the latter insisting otherwise. A bewildered Yozora is then taken aback by Sena asking her to be her friend, only to be confirmed by Yozora of there already established friendship.
As Sena and Yozora grew closer as friends, the two still continue to view each other as love rivals vying for Kodaka's affection, though bearing no ill-will . Sena showed her concern towards her best friend when she tried her hand in helping with Yozora's dysfunction family situation by hiring her as their estate's butler. This would, in turn, lead to Yozora meeting Stella, the estate's current butler at the time, and eventually idolizing her, much to the envy of Sena.
Sena initially saw Kodaka as just another one of the boys that tried to win her attention. As such, she would sometimes make fun of Kodaka and offer Kodaka her "reward" of stepping on him, or something similar. To her surprise, Kodaka did not want her rewards and didn't act like the boys she usually knew. Because of this, Sena's insults to Kodaka toned down significantly and she began to view him differently.
Sena soon began to trust Kodaka more and more as she believed that Kodaka would keep the promise to teach her how to swim and wouldn't tell anyone that she secretly likes her nickname "meat". After Kodaka scolded her for being foolish and arrogant, Sena was shocked to know that she was actually scolded by a guy her age. 
Slowly, Sena started to harbor feelings for Kodaka and was shown to be especially embarrassed by the fact that Kodaka saw her naked (twice) . She was rather unhappy when she could not kiss Kodaka directly at the "King game"  and even hinted to Kodaka that she liked being in his company (which Kodaka had no caught on at the time) . She was shown to be romantically competitive, always stating that she will not lose to the likes of Yozora in vying for Kodaka's affection. When their engagement was made known, Sena agreed to the idea of being married to Kodaka (masking the fact by stating she wanted to be true sisters with Kobato) and expressed disappointment when Kodaka dismissed it ; however, Sena nonetheless confessed Kodaka her true feelings.
Fortunately, for Sena, Kodaka was also romantically (and physically, to an extent) attracted to her, however, Kodaka was particular about not dating anyone from their club and insisted Sena to wait for him until they graduate high school; Sena agreed to Kodaka's wishes out of her love for him . However, when Kodaka broke his aforementioned promise by dating Yukimura and knowing his intentions of leaving the club altogether , Sena lamented at one point but continued to romantically pursue Kodaka, demanding that he remain in the club and allow himself to be fought over by her and Yozora .
Sena seems to like Kobato a lot (main reason being her cuteness) and always tries to get on Kobato's good side. However, this feeling is not mutual and Kobato would often cry and hide behind Kodaka, seeking protection, and reject Sena's offers and suggestions. Sena however, doesn't seem to be bothered by Kobato's cold attitude and even has been shown to be delighted at Kobato's insults.
As the series progresses, Sena's obsession with Kobato begins to grow to extremely creepy levels, from wanting to bath with Kobato to even more immoral things like trying to lick Kobato and saying how she wants to legally molest her which made Kodaka feel uneasy.
Sena was soon under the delusion that Kobato is her younger sister (much to Kodaka and Kobato's annoyance).
Sena and Rika are on reasonably good terms with each other and as some of their interests happen to intersect (galges), they share tips on playing dating Sims and discuss games in general, especially at times when Yozora starts to show her ignorance in these topics. However, at times, Rika changes sides, and joins Yozora in her pranks and bullying of Sena (due to being jealous of Sena's beauty or simply because Sena is way too naive in some matters).
Yukimura and Sena do not interact with each other often but Sena does seem to treat Yukimura more or less normally (Even when she thought that Yukimura was a boy). However, when Sena was shown to be quite good at being a maid, Yukimura was slightly jealous and became very angry when Sena flaunted her buxom body.
When she revealed herself to be Kodaka's girlfriend, Sena took it as a challenge in competing for Kodaka's affection. 
Sena seems to have a soft spot for Maria (probably due to being able to empathize her for Yozora's trickery to Maria) and was shown to buy Maria a ticket to the theme park and even helping her become a temporary adviser, after being pointed out that she wasn't a sister or a teacher in the first place. Though she may have only done this only for the sake of the club (or to get back at playing with her video games)
Student Council membersEdit
At first, Sena doesn't seem to show any ounce of interest towards Aoi after Kodaka mentioned the latter to her. Despite having known that Aoi holds her at high esteem, and at the same time, animosity and a sort of rivalry towards her, Sena still couldn't care less about the latter, as Sena once noted that she never knew the names of the majority of her female classmates . Though when Aoi suddenly shows up before the Neighbor's Club in an attempt to disband it , Sena confronts Aoi with pure hate and threatens the young girl to expulsion from the Academy, leading Aoi to surrender in tears .
In many ways, Sena and Aoi cannot maintain a mutual relationship in the course of the times they've interacted mostly because of their differences and views to one another.
While initially forgetting about her at first, Sena forged a mutual relationship with Hinata when her best friend (younger sister, in Hinata's case) expressed her attraction towards Stella, the Kashiwazaki estate's butler. This caused them to share a common trait in dissing Stella.
As her father, she loves, respects, and doesn't mind getting scolded by him. Since he's a father, he's always busy with his work. Their interactions with each other are limited. She also seemed to be glad whenever her father is in a good mood, which usually ended up of him getting drunk.
On the surface, Sena's relationship with Stella is depicted as that of a master and servant. Sena being heavily reliant on Stella for her needs, particularly her appearance and clothing . However, Sena is aware of her half-sibling relationship with Stella and their interactions as sisters are mostly unknown, though it can be assumed that they are fairly close.