Legend of Izaron

This is a tale from when mankind and nature had not yet parted. In the country of Izaron, which was hidden away by an ocean of foliage, there were two princes. The child of the king, Tiokia, and his brother's child, Rukishu, spent their childhoods as "prototypes"- they were neither princes nor princesses, as was characteristic of Izaron. As time passed, Rukishu became a prince, while Tiokia stayed physically androgynous. The country became conflicted as to which should ascend the throne as they aged, and the siblings' bond was severed as a result. In this timeframe, Tiokia gets sent to a neighboring country as a hostage as ordered by Izaron's king-!

(from mangaupdates)