Aisuruhito wo Korosu Toki, Watashi wa Nani wo Omoudarou

On the night of her 14th birthday party was when it all began. Her country was attacked by the imperial army, led by a man in armor, slaughtering the people. Her beloved mother was killed by the Man in Armor right before her eyes. Erica, the only survivor, vows to kill the "Man in Armor" who took away her mother and friends. Erica finds solace in a boy she meets by chance, Raoul, whom she befriends. The two gradually become attracted to each other, but Raoul's true identity is the "Man in Armor." This is the story of Erika and Raoul, who grow up together while facing their pain, until they can find common ground.

(Souce: LINE Manga, translated)