The founder of the Tobu once decided to removed the separation between his chakra and that of his companion. The result was a powerful new half bird half human form. He decided however, that due to the danger it imposed it would be forbidden to all but the best trained Tobu.
The user and their bird(s) meld their chakra and bodies together, reaching the ultimate form the Tobu can hope to achieve; The Tengu. A mix between human and bird, the user gains the ability of limited flight, enhanced maneuverability as well as being able to fuse chakra into their feathered arms to use them like blades.
Short Distance flight.
Blade like feathers cover their arms.
Enhanced reflexes and perception.
Access to new jutsu techniques
Constant and heavy drain on the user's chakra reserve.