You:ve been chosen by the Yatsurugi-gumi to become Touka's bride & to give birth to her child, so that she can take over the Clan as their new heiress.

A lot of big things are happening to the Yatsurugi-gumi Clan. Touka's graduating High School, Kotaro's giving birth to his 3rd baby, & you're getting married into the family. 

During your time with the Yatsurugi-gumi, you'll either interact with your future bride, your new family members, or other pregnant husbands in the Tokyo community.