Senkou

A Second-Year at Gessen Girls' Academy, Senkou is a brooding, cold and no-nonsense girl that rarely interacts with her peers. Commonly mistaken for twins, Senkou is in fact Gekkou's half sister, a result of two mothers and one father, and is the eldest by one month.

While Gekkou is friendly and likes talking to people, Senkou prefers to hang behind her sister and act distant to everyone. This is merely a front, however, as she is very close and warm when alone with her sister, though she can still be thrown off by Gekkou's hair-brained plans.

She is a chuunibyuo, often giving herself names like the 'Princess of Darkness' and makes her attack names overly dramatic. Unlike the anime, she is a high schooler as well, but she certainly acts like she's in middle school.

Senkou also tends to be Gekkou's muscle in many situations, often being relied on to either do a lot of heavy lifting or look tough, as Gekkou herself can't really pull it off.