Aina is beyond beautiful in appearance and build, with short dark blue hair and a relatively flat chest (of which she is extremely self-conscious). She dresses in fairly simple clothing.
When she's Cakey, she sports a blond wig kept in long pigtails and extremely thick "cakey" makeup which makes her unrecognizable. She also tends to dress more gaudily and is more comfortable showing skin.
Aina's personality changes drastically depending on whether or not she's her regular self or if she's in her Cakey get up. When she's normal, she's notably shyer and more soft spoken. She has low self-esteem when it comes to her appearance, especially the size of her breasts and she is extremely envious of Nanaka Kotegawa and Azusa Hamaoka as they both have extremely large busts. Aina is a bit of a romantic compared to the other characters and she has noted that she seems to be the only person in the club who ever thinks about love and romance.
As Cakey, she is much more confident and bold, with excessive and flamboyant body language. She asks out Kouhei Imamura upon meeting him on account of his attractiveness and when drunk, she gets touchy feel and violent.
- Iori Kitahara: Aina has romantic feelings for Iori due to him sticking up for her when she is picked on. They are friends and members of the same club.
- Kōhei Imamura: Aina and Kohei are both part of the diving club and are friends, though they do not have that many interactions. When they first met, Aina asked Kohei out due to his good looks, but she now harbors feelings for Iori. Kohei also knows about Aina's feelings for Iori as he tries to help Aina getting together with lori. During the hypnotization of Kouhei, it is now shown that Aina is on the receiving end of Kouhei's love for anime.
- Ryūjirō Kotobuki: Her senior, Aina finds it hard to keep up with Kotobuki's rowdy behavior and has a particularly hard time dealing with his almost constant nudity. However, they are members of the same club and are on good terms.
- Shinji Tokita: Another one of her seniors, Aina's relationship with Tokita is similar, if not, identical to the relationship she shares with Kotobuki.
- Chisa Kotegawa: Aina and Chisa are friends and hang out regularly. Aina is envious of Chisa's relationship with Iori and often becomes downcast when Chisa and Iori are close. Chisa does not seem to be aware of Aina's feelings for Iori.
- Azusa Hamaoka: Like with Kotobuki and Tokita, Aina is often exasperated by Azusa's mischievous and energetic personality, particularly her stripping and partying habits. Azusa likes to tease Aina and seems to be somewhat aware of Aina's feelings for Iori. Aina is also jealous of Azusa's physical attractiveness and large bust and becomes particularly flustered when Iori and the others are attracted to Azusa's body.
- Sakurako Busujima: Aina has taken a clear dislike to Sakurako ever since their first encounter, as she misunderstands Sakurako's relationship with Iori. She becomes extra alert whenever those two are together, or when there are hints of Sakurako's affections towards Iori, as shown during the lie detector test.
Grand Blue Employees:
- The name Aina means "love, affection" (愛) (ai) and "vegetables, greens" (菜) (na).
- Aina's surname Yoshiwara means "lucky, good" (吉) (yoshi) and "field, plain" (原) (hara/wara).
- Aina is nicknamed "Cakey" due to the large amount of makeup she used to put on her face in an attempt to be more popular with guys
- Aina loves to watch love dramas, and often has open thoughts about romance
- She joined the tennis club because she heard it's the easiest place to get a boyfriend