Saionji Itsuki, a 38 year-old single woman who works for an app development company. She excels at her job, having created a hit number of apps, and is known for her bright, positive attitude and strong communication skills. She enjoys her single life without domestic chores, but everything changes when she suddenly ends up having to share her home with Kusumi Toshinao, an unfriendly genius engineer who has just transferred to the company, and his four year old daughter, Ruka.