Board Thread:Game Discussions/@comment-25252144-20151116112652/@comment-27862737-20161010141900

On Gree's own page it says that moving from one to the other (either Android to iOS or vice-versa) is actually a breach of their ToS agreements, since they are different operating systems:

https://games.gree-support.net/hc/en-us/articles/203406874--Can-I-talk-to-friends-add-friends-or-switch-my-account-from-apple-Android-or-Android-Apple-