Kamisama To Tobenai Tsukai summary:

Shin, born to a race of winged messengers, faces life as an outsider due to the tiny deformed wings on his back. Flightless, he endures ridicule and loneliness. His people tend to the needs of the Gods who reside in the same mountains, and unexpectedly, he is tasked with the care of the mysterious God residing at Mountain 32. A troubling future looms ahead as Gods and Messengers have begun to disappear without trace. What danger awaits Shin and his people, and the Gods they care for?