He has a overwhelming fear of being alone. 

Atsushi's traumatic past affects much of his daily life, and he is tormented with nightmares, flashbacks, and the internal monologue of the orphanage director who abused him. He has a severely low sense of self-worth and is somewhat naïve, which causes him to initially feel helpless when confronted with dangerous situations. When paralyzed in guilt and/or fear, he has difficulty reacting or understanding what to do.