Grimgar of Fantasy and Ash (Light Novel), Vol. 09

As the battle against the orc Jumbo and his group Forgan descends into utter chaos, the party faces a crisis unlike any before: Ranta has betrayed them to join Forgan. From there, they are split up again and fight an intense retreating battle. Not knowing where their friends are, or if they're safe, Haruhiro and his comrades must face the greatest challenge of all in the misty Thousand Valley-being alone!