Answer: Paranoid personality disorder.
Explanation:
Paranoid personality disorder is the disorder in which a person tends to mistrust others, doubt others intention, motives,loyalty etc, believes people have suspicious behavior and thoughts and show anger and social detachment .These beliefs arise from suffering persons' mind even though there is no reason to doubt others.
According to the question, Herman is suffering from paranoid personality disorder as he doubts his friends motive that they have hidden intention of hurting him or some other suspicious behavior against him.He has few friends because of this falsely accusing behavior .