This is book #3 in the award-winning Faith & Kung Fu series by T.M. Gaouette
 
The world continues to press in on Gabriel Livingstone’s quiet life when fifteen-year-old Aaron Buckley enters Yeung’s Martial Arts Studio looking to learn kung-fu. Gabriel knows there’s a desperate secret behind the boy’s bruises, and secretly vows to be his guard, with the help of his friend Christian. But when Tanner Rose pressures him for strength and direction, and Faith’s continued rebellion send him and his friends to the hospital, jeopardizing Tanner’s career, Gabriel is forced to reexamine his decisions. Is he called to the priesthood or is life behind the monastery walls merely an escape? 
“Finally, be strong in the Lord and in the strength of his might. Put on the whole armor of God, that you may be able to stand against the wiles of the devil.” (Ephesians 6:10-11 RSVCE)