When is the full version (4 mins) ending song of the anime god eater releasing? I have been searching in different websites but I could only find the short version of kouhaichi.
Full anime ED, OP and Soundtracks is always first come in Bonus CD inside Blu-ray Collector Edition. So, if you want a full version of ending song for example, you need to wait for the release of the Blu-rays.

God Eater just finished airing recently, I don't know the Bonus CD will be packed inside which volume of the Blu-ray. An anime with 13 episodes like God Eater is usually sold separately with 7 volumes, while Vol. 6 is released just a week ago, Vol. 7 will be released on April 21th. Maybe a week or so after the release of all volumes, some websites might provide contents in the Bonus CD on their site, not sure whether it's legit or not.