(大切なことはすべて君が教えてくれた)is a January 17, 2011 -- Japan.

Plot

Natsumi Uemura ( Erika Toda ) is an English teacher at Meiryo High School. She has always dreamed of being a teacher. Until her middle school days Natsumi lived in the U.S. She is now a first grade home room teacher and advisor to the basketball team. She is bright and has a positive character, so she is popular with the students. Shuji Kashiwagi ( Haruma Miura ) is a biology teacher at the same high school. Shuji is a 2nd grade home room teacher. Shuji is faithful and considerate. He deals with students with his heart so not only students but also their parents support him completely.

Natsumi and Shuji graduated from the same high school and university. They plan to marry in 3 months. Natsumi's friend and roommate, wedding planner Sayaka Todo ( Mariko Shinoda ), helps the couple with their wedding plans. All signs point to Natsumi and Shuji being happy.

On the first morning of the new school term, Shuji finds a naked woman sleeping next to him. Shuji thinks back to the prior night and recalls becoming drunk and having sex with the woman. He becomes embarrassed, but gives the unidentified woman a key and leaves for work. Shuji feels guilty to Natsumi and regrets what he did, but tries to calm down and prepare for the new school term.

Students in the 2 grade 1 class like Shuji as their home room teacher. When Shuji calls roll he discovers two students, Hikari Saeki ( Emi Takei ) and Nozomi Sonoda ( Ayame Gouriki ) have not yet come to school. At that time, one female student walks into the class room. The girl is Hikari. Shuji tells the students to move to the auditorium for the opening ceremony of the new school term. Hikari stays in the classroom until the rest of the students clear out. Hikari gives something to Shuji. The item is Shuji's apartment key. Shuji realizes the woman he spent with last night is Hikari ...