Hmmm... The game is just over 2gb in size, both with the .apk and unpacked. In theory, you should only need 4gb free at the most.
There is an unofficial compressed version of the game that sits around 500mb over on F95zone - unfortunately I can't link it here on Itch due to their rules, though. DM me via Discord (Maelstrom507) and I can send you a link there? :)