This iPhone 5 Case (￥4,980Prices are approximate only and subject to change.
White Rabbit Express service fee and other costs not included.) by Thanko has a built-in charger. When attached to the phone it dramatically increases the viewing time of videos and other battery-consuming content, that usually quickly depletes the battery.

Since it’s only 14.6mm thick, there is not much extra bulk to carry around and the additional 70g are hardly noticeable. It also comes with a micro USB cable and has perfectly placed recesses for the headphone jack and the operational buttons.

The black model is matte and the white model features a glossy finish.

Specifications:
Size: 14.6 x 62.3 × 136.5 mm
Weight: 70g
Accessories: Charging and synchronization micro USB cable
Battery Type: Lithium polymer
Compatible models: iPhone5
Input and output: 5V, 500 ~ 1,000 mA
Charging time: About 3 hours (case)
Battery Capacity: 2,600 mAh

Please note: Compatible with iOS 6.0.1, may not be supported by future updates
Warranty: 6 months