World Break: Aria Of Curse For A Holy Swordsman Vol. 16 (Light Novel)

Akane Academy is a school that trains students with special powers called Saviors who fight against monsters that threaten humanity called Metaphysicals using Ancestral Arts. Saviors are special in that they are able to recall memories of their past lives, and they are divided into two groups: Shirogane (White Iron), who are able to manifest weapons and martial techniques, and Kuroma (Black Magic), who are able to use defensive magic.
Moroha Haimura is a 15-year-old student at Akane Academy who possesses a special gift: he is able to recall memories from two past lives, making him the first Savior in history to be both a Shirogane and Kuroma. At the academy, he meets Satsuki Ranjo, a boisterous and boastful girl, and Shizuno Urushibara, a quiet and level-headed girl, who each have a special connection to him. Turns out, Satsuki was his sister in a past life and Shizuno was his wife! Even though he just wants to have a peaceful school life, that all goes out the window when Satsuki and Shizuno begin vying for his affection, and things only get worse when Metaphysicals start appearing!
In Vol. 16, summer break arrives for the second-year students, and Moroha and friends head for a training camp arranged by Russia’s new representative, Katia. However, they receive disturbing news from Edward that nine officers from the Russian branch have mysteriously disappeared and hints that Katia may be connected to the Six Wings Conference. Moroha is given a secret reconnaissance mission by Edward to gather intel, but with only three days to do so, will he be able to uncover the conspiracy?
Notice: This book is written in Japanese.