DeNA has announced a brand new Hunter x Hunter mobile game called Hunter x Hunter Arena Battle (HUNTER×HUNTER アリーナバトル). Together with this announcement, they have release a new teaser website together with an official Twitter account.
There are no information on how the game is like for now. What we do know is that they have release a teaser site for Players to solve some puzzles and a countdown page. I believe more information about the game will be released when the countdown strikes 0.