My Wife is a High School Girl (2005)

The 17-year-old Onohara Asami is a cute, second-year high school student. Nobody knows that she is actually already married to her 25-year-old physics teacher, Ichimaru Kyousuke (Danna-sama). Besides her responsibility as a student, she now has to take care of the household and keep the marriage a secret at school. Juggling these things on a daily basis is all but easy for Asami, especially with the complications introduced by her well-meaning but nosy best female friends; an overprotective very intrusive father Iwao; the kind teacher Iwasaki who of all men falls for Asami's husband; or the quite alluring next-door neighbour Sakura Mizunosaki. Against all these odds Asami tries to nurture her young love with Danna-sama.