Boku no Ie ni Oide Wedding

From Endless Journey:

Mirei, an 18 years old studying as a specialized student in design, was proposed to by Mano during her high school graduation. Now preparing for her wedding in the summer with a handsome high-class man, this marriage seems like a dream. In reality, these two haven’t even taken their relationship into adulthood yet! How will the naive Mirei handle their newlywed life?