At present, you can buy it on Booth or DLsite,and Mofu sensei said that after completing Futaken Valley, he might upload futaring on itch.And Futaring will be updated in the future, but after Futaken Valley is completed, Mofu sensei has a plan to remake the game and will update some new content. I am also looking forward to it and I like the Mofu's works very much,it's really worth to replay.