They can get bored fast and are consummate escape artists. These dogs need human companionship and want to be with you constantly. After all you can't protect your person if you are not with them. If you must keep your Akita in a yard I would suggest a large pen and shelter from the sun (with a fan or they can overheat). The pen should be large enough for the dog to exercise, set in concrete so they can't dig out and tall enough that they can't clear it.
Akitas will get bored in a yard, and possibly try to escape. Also, you must make sure that the area is a quiet area and the fence is secure, since not only will Akitas try to escape, they are also natural guardians. You could have a problem on your hands if a neighbor or another dog comes into your yard. In addition, Akitas require socialization and companionship. The independence and stubborness of the breed may turn into aggression if left alone without proper training and socialization. I have had Akitas roaming 2 acres of land and Akitas living in a small one bedroom apartment, and the Akitas who lived in the apartment were more responsive and friendly animals. Finally, Akitas (and most dogs) will not exercise themselves. They will find a place to lay down and wait for you to come home. If they do get "exercise" it will likely be in the furtherance of undesirable habits (digging, hunting, chewing, etc.) Therefore, even if you have a yard, you must make time to walk you dog - promoting both bonding and exercise.