Rena Kariu

Rena Kariu (狩生 玲奈, Kariu Rena), later Rena Ōga (大神 玲奈 Ōga Rena) in Vol.15 Chapter 225.5, is Arata Kaizaki's classmate who sits beside him after he became a teenager, a member of the girls volleyball club at Aoba High School and the girlfriend of Kazuomi Ōga who later becomes his wife at the end of the manga.

Appearance
Rena is a slim and well-developed girl with with shoulder-length brick-colored hair that is tied into a single ponytail on the left side in a grey ribbon with bangs that curtains her face where it nearly covers the right side of her face, blue-grey eyes and an average build.

She is mostly seen wearing her school uniform though she does wear her gym clothes while practicing for volleyball.

Personality
At first, when Arata Kaizaki meets Rena, she is quite judgmental considering how on the first day he was caught with cigarettes in his bag, but she is considerate enough to lend him a pencil and eraser when he needed.

She is also a very stubborn and competitive girl who is shown to be quite determined as she came to the first day of school, sick, in order to beat Chizuru Hishiro in the exams and become a student council rep for the class.

Rena also has trouble expressing her feelings at times and will consider avoiding them or trying to cause others the same misery she's feeling such as when she tried to steal Chizuru's bag.

History
In middle school, Rena watched Honoka Tamarai play volleyball and soon accused her of holding back. After several taunts, Tamarai reluctantly smacked the volleyball straight for Rena; knocking her to the ground.

Story
On the first day of school, Rena notices Arata Kaizaki panicking after realizing he had forgotten his pencil box. She soon hands him a spare pencil, annoyed that someone his age would easily forget something so simple.

After the tests, Kaizaki thanks Rena for helping him as the two begin to talk. It is soon revealed that Rena has a slight cold, in which Kazuomi Ōga recommends that she should have stayed home. However, Rena states she is perfectly fine and wants to pass the exams in order to achieve the spot on the student council representative and receive the class pin.

Arata Kaizaki
Kariu's first impression of Kaizaki is that he was an idiot (because he brought cigarettes instead of a pencil case on the first day) but as the story progress, she was able to be friendly to Kaizaki as they continue to interact.

Honoka Tamarai
Rena and Tamarai have been friends since junior high after Tamarai transferred in order to start fresh.

Chizuru Hishiro
Rena has considered Chizuru her academic rival since the beginning of the school semester, after losing to her during the exams. She soon begins to loathe the latter as she notices Chizuru hanging around Ohga a lot more while the two tend to the student council work. The two later become friends after Rena nearly steals her bag and apologizes after being caught by Kaizaki.

Kazuomi Ōga
Kariu has had feelings for Ohga ever since their time in middle school that she even had matching piercings with Ohga during this time. During the summer vacation, she decides to confess her feelings to Ohga, but he confesses his feelings first and they decide to become a couple after being bashful for a while.

In Vol.15 Chapter 225.5, they eventually got married (which now makes her Rena Ōga).

Quotes

 * "I can't help being competitive. I always want to be first."

Etymology

 * The name Rena means "the tinkling of jade" (玲) (re) and "apple tree" (奈) (na).
 * Rena's surname Kariu means "hunt/hunter/hunting, raid, gather" (狩) (kari) and "life, living" (生) (u).
 * Kariu is an homage to Kariu Station.
 * Her married name Ōga means "big, great" (大) (ō) and "god" (神) (ka/ga).

Trivia

 * Rena likes to consider Chizuru Hishiro and Honoka Tamarai as her rivals in Studies and Volleyball respectively.
 * Rena and Kazuomi Ōga both have matching piercings in their ear.