My Big Sister Lives in a Fantasy World: Volume 2 by Tsuyoshi Fujitaka

Yuichi hasn't yet unraveled the secret behind his magical sight, but the end of his first school term is still as busy and can be! He's got survival club activities led by his big sister Mutsuko, early morning combat training with the serial killer Natsuki Takeuchi, and a first date with the vampire Aiko Noro (with his little sister tagging along, for some reason). Then, in the midst of it all, Aiko reveals that her big brother Kyoya – whose world domination-plotting middle school syndrome has been growing worse and worse lately – has gone missing!