Genkaku Cool na Sensei ga Aheboteochi!  

엄격하고 쿨한 선생님이 아헤보테오치, 厳格クールな先生がアヘボテオチ!

At school, there's a well-liked instructor named Hazuki Mizushiro. On one occasion, pupil Aoi mustered the bravery to compose a romantic missive for her. To his delight, she answered back.