Wolf fang over fang

Wolf fang over fang
http://images4.wikia.nocookie.net/naruto/images/thumb/d/d4/Man_Beast_Combination_Transformation_Double-Headed_Wolf.jpg/180px-Man_Beast_Combination_Transformation_Double-Headed_Wolf.jpg

kiba and Akamaru Combin with each other to make a double headed wolf creature ,which increases the power of both of them but they can only use it a few times.The chakra