Arisa Ishino (石野 ありさ, Ishino Arisa) is a classmate of Hikari Tsutsui and Iroha Igarashi who was initially annoyed and disgusted on Tsutsui's otaku lifestyle, but she became friends with the two and joined the gang later on.
Arisa has chest-length light-peach hair (her hair reaches to her hips when she styles it down) that is tied in a ponytail with bangs swept to the left where it is sometimes swept to the right side and dark peach-brown eyes.
Seven years after leaving high school, she cuts her hair to chin-length.
Arisa was one of the first friends to Hikari Tsutsui, bonding with him in grade school after learning he was good at drawing anime style. However, when he continues the hobby into middle school, she pretends she never knew him to preserve her reputation. She also begins trying to get a boyfriend, but her poor judgement leads her to date many lousy guys who take advantage of her.
In high school, Arisa starts interacting with Hikari Tsutsui after running into him by accident. Unable to stay out of his and Iroha Igarashi's business, she becomes a sort of confidant for them to bounce their problems off of. She also tries to woo Mitsuya Takanashi, even though he shoots her down repeatedly.
At first, Arisa met Mitsuya after he was apologizing for all his misdeeds against Hikari Tsutsui and instantly finds him attractive. She openly shows her attraction to him much to his dismay, but after spending time with each other, Mitsuya begins to care for Arisa even if he doesn't show it. He eventually develops feelings for her and makes her his girlfriend.
Arisa stays with him long after high school, but her bond with him is anything but smooth. Over the course of seven years, they break up and get together again repeatedly. After her on again, off again relationship with Mitsuya results in her getting pregnant, she finally resolves to marry him, making her Arisa Takanashi. After their wedding, she later gives birth to a baby boy.
- Ishino - by Mitsuya Takanashi
- The name Arisa is written in katakana (ありさ), which has no special meaning. However, when written in kanji (有沙 or 有紗), it could possibly mean:
- 有沙 - "exist" (有) (ari) and "sand" (沙) (sa).
- 有紗 - "exist" (有) (ari) and "thread, silk" (紗) (sa).
- Arisa's surname Ishino means "stone, volume measure" (石) (ishi) and "field, wilderness" (野) (no).
- Her married name Takanashi means "tall, high" (高) (taka) and "pear" (梨) (nashi).
- Arisa is Iroha Igarashi's first female friend.