間宮 八雲

What she calls the protagonist: Ryou-chan

The oldest daughter of the Mamiya quintuplets and a very outgoing and popular girl, she always has a group of people around her. She also has excellent grades and is good at all sports, but she loves swimming the most, especially swimming in the ocean. She does have her clumsy side too. In fact, Yakumo is a very clumsy girl, but she does her best to hide this fact from Ryouta, and look like the perfect older sister in his eyes.

Like Tamane, Yakumo is not part of any club and instead, spends most of her free time working as a waitress at Seamore. Thanks to her assistance, the sales have raised up and she is quite popular with the customers as well, offering lively and good service to them.

Like her sisters, she also has a some kind of a kink related to Ryouta. Yakumo has the voice kink, meaning that she immediately turns on whenever Ryouta whispers anything or just sweet nothings to her.