Takahiro Arai missed practices on October 5 because he was not feeling well. He was taken to a hospital in Hiroshima for tests and diagnosed with tonsillitis.
Source: Nikkan Sports 10/5/2017
[UPDATE 10/9 @ 9:12pm]
Arai resumed workouts at the indoor training facilities at Mazda Stadium today.
Source: Daily Sports 10/9/2017