The 28-year-old Japanese international will wear the number 12 shirt at Eibar.
— SD Eibar (@SDEibar) September 16, 2020
But in two seasons with the Magpies, Muto made only 28 appearances, scoring two goals.
With Newcastle bringing in a new striker, Callum Wilson, the club decided to let Muto go out on loan.
Newcastle boss Steve Bruce said: “He hasn’t really played a lot and with the additions we have brought in this year, we think it’s best for him to go and play somewhere where he’s going to enjoy his football.”
Muto will spend this season in La Liga with Eibar, where he will link up with fellow Japan national team player Takashi Inui.