Taisetsu na Koto wa Subete Kimi ga Oshiete Kureta (2011)

Description:

Toda and Miura play two teachers, Natsumi Uemura and Shuji Kashiwagi, at the same high school who are set to get married in half a year. However, the night before the school year's opening ceremony, Shuji becomes involved with the young Hikari Saeki (played by Takei), without realizing that she will be a student in his class starting the next day. As Shuji struggles to help Hikari deal with the mental complex she is suffering from, he is also torn inside by his betrayal of Natsumi. Meanwhile, Hikari attempts to get closer to Natsumi, driven by feelings of jealousy and a desire to destroy the couple's relationship.