Machigaigoto 

"Our relationship began with a mistake." Kagami Yuuko wakes up in an unknown man's bed. She was picked up by Azuma when she passed out on the street after going drinking. She gradually warms up to him and falls in love with Azuma, but they both re-encounter each other in high school! Turns out Yuuko is a high school student and Azuma a teacher. What will be of this relationship full of mistakes...?