From MangaHelpers:

Amano Chiharu goes to a school where students are assigned into couples, in order to learn how to become good husbands and wives. Many pairs end up actually getting married after their school years. However, Chiharu's 'husband' broke up with her in their third year, saying that she talked too much about games and was useless at being a wife. Chiharu decided that she didn't need a husband, and that she would pursue her dream of making games.

Then one day, Kasaki Kaname, a younger student in her school, became her new partner. She tried to keep him at arm's length, but he was very determined that they would become an actual couple. Chiharu is into younger men, and though Kaname doesn't look younger than her, she likes how he sometimes looks up to her for guidance. Also, since Kaname was born and raised in America, he has no problem with the idea of Kaname pursuing her career dreams after their marriage. Could Chiharu's second 'partner' really be the one for her? [tethysdust]