As a player who has played this game for over a month, I'm disappointed in January's sign in ninja. Players who played longer have more gnw ninjas.
IMO, keeping great ninja war ninjas as a monthly sign-in reward is win-win for players and oasis games. Players can get them at 2 or 3 stars for free. Potential spenders can try them out and may feel enticed to buy fragments to upgrade them when they show up again in time limited events.