Arthur Brennan, a grief-stricken American man, travels to Japan's Aokigahara Forest, famously known as the "Suicide Forest," with the intention of ending his life. Wandering deep into the dense wilderness, Arthur encounters a Japanese man named Takumi Nakamura, who is also contemplating suicide. The two men, despite their language barrier, form a desperate bond as they decide to navigate the perilous forest together, seeking a way out. Throughout their journey, they share their stories and reasons for their sorrow, which creates a deeper connection between them.

As they struggle to survive against the harsh elements and their own emotional turmoil, Arthur begins to reflect on his life back in the United States, including his tumultuous relationship with his wife, Joan. The journey through the forest becomes a path of self-discovery and redemption for both men, unraveling deeply buried emotions and leading them to a critical realization about their lives. Their newfound friendship transforms their perspective on life and death, driving them to find meaning and hope in the most unexpected of circumstances.