Final answer:
In 'The Truth as Told by Mason Buttle,' Mason's new best friend is Calvin Chumsky, who provides him with much-needed support and companionship.
Step-by-step explanation:
In the book The Truth as Told by Mason Buttle, Mason's new best friend is a boy named Calvin Chumsky. Calvin is the one person who understands Mason and accepts him as he is, despite Mason's learning disabilities and the tough circumstances he endures. Calvin's support and friendship play a significant role in Mason's life, providing him with the companionship and understanding that he desperately needs.