Living With My Pupil Is Even More Stressful Than the Battlefield is a Manga/Manhwa/Manhua in english language, ONESHOT series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

Toudou Soujurou is a former mercenary instructor who has survived in a war zone with his student, Sylpha. After the war, Soujurou takes in the lonely Sylpha and returns to his hometown in Japan, where he suddenly realizes that he had a crush on her. However, thinking of Sylpha who can live as a normal girl from now on, decides to step aside, but to his surprise, Sylpha also confesses that she likes him... A love comedy about a former mercenary instructor and his student living together!