Oka

, affectionately referred to as, is a high school student who attends Saint Ishiyama Academy where she has participated in the school's special event, Saint Saint X'mas, with her boyfriend, Mitani.

Appearance
Oka is a slender, young girl with full lips.

She has long, light-colored hair and dark eyes with long eyelashes. Her hair is messy and wavy, reaching down to the middle of her back, while her short bangs fall upon her forehead and the rest beside her ears.

Oka wears the uniform of Saint Ishiyama Academy while she is at the high school, like several other students. She wears a light-colored shirt slightly unbuttoned, revealed a slight portion of her cleavage, and a bow wrapped around the collar. Over this, Oka wears a light-colored sweater and a dark skirt. She wears dark socks that reach just below her knees and top off her outfit with light-colored shoes.

Personality
Oka is a very affectionate and intimate person, especially towards her lover, Mitani.

However, Oka is also rather competitive to the point where she becomes very arrogant. She constantly taunts her opponents, Hajime Kanzaki and Yuka Hanazawa, upon first meeting them while at the Saint Saint X'mas competition. Oka becomes angered when they seemingly violate the rules using physical attacks. Later, she becomes more mean towards Mitani, referring to him as an "idiot" for becoming careless after the particular incident.

Saint Saint X'mas Arc
Oka and Mitani participate in the Saint Saint X'mas competition together where they advance to the Top 16. The couple is selected to go second in the first round, putting them against Hajime Kanzaki and Yuka Hanazawa, who have picked first.

The couple proceeds to complete their first round; however, after watching their opponents from the previous event, Oka is being carried by Mitani throughout the rest of the tournament. When meeting with their opponents, Oka tells them that they are mistaken if they believed that no one else knew about the princess carry technique.

Oka and Mitani head to the boxing ring in the gymnasium for their first event, and while Oka is being affectionate towards her partner, they discover that they will need to share drinks from a bottled drink for them to advance in the tournament. Seeing the reactions from Kanzaki and Yuka, Oka suggests that they give up while they have the chance.

Afterwards, the event commences and Oka intimately pours the drink in Mitani's mouth. While pouring, they are suddenly attacked by Kanzaki and Yuka, though Oka is unhurt; nevertheless, she becomes angry and wonders whether it is against the rules. She and Mitani then resume the event for themselves where Oka briefly scolds Mitani for being distracted. Unfortunately, moments later, they are attacked by a thrown Kanzaki, forcing the two lovebirds to pass out and ultimately lose in the first round.

Mitani
Mitani is Oka's boyfriend whom she competes with during the Saint Saint X'mas competition. Although she is very affectionate towards him, she is not above insulting him when he displeases her, such as when he pays little attention to winning an event.

Etymology

 * The surname Oka means "ridge, hill" (岡).