Okusama wa ShougakuseiMy Wife Is an Elementary Student; Oku-sama wa Shōgakusei; 奥サマは小学生; 我的老婆是小学生

The story is set in the near future when the marriageable age was lowered in response to the declining birth rate. A 24-year-old man marries a 12-year-old girl in this gag comedy.