Arthur Brennan (McConaughey) goes to Japan to commit suicide in a forest knows as the perfect place to die. There, he meets Takumi Nakamura (Watanabe), a guy who tried to kill himself, but changed his mind and now tries to get out of the forest. Soon, Arthur changes his mind too and he decides to help Takumi to get out of the forest.
The Sea of Trees provides examples of:
- Awful Wedded Life: Joan and Arthur constantly quarrel (because she drinks too much, because he does not make enough money, because he cheated on her).
- Book Ends: The film begins with Arthur's plane travel to Japan. He does not eat anything on board. In the end, he comes back home by plane and eats an omelette on board.
- Bungled Suicide: Takumi slashed his wrists, but he survived.
- Chekhov's Boomerang: The names of Takumi's wife and daughter. Takumi tells Arthur about them early in the film. When Arthur is rescued, he remembers these names and the fact that the authorities cannot use them to identify Takumi is an important clue that Takumi does not really exist. Finally, a student of Arthur tells him that these are not Japanese names, but translations for "yellow" and "winter", which means that Takumi was probably Joan's spirit.
- Chekhov's Gun:
- Takumi and Arthur discover an orchid in the forest. Takumi says that a flower grows when a soul has crossed over from this place. In the end, Arthur discover another orchid in the place where he left Takumi.
- Takumi tells Arthur that the song he sung, Rakuen eno kaidan, means "Stairway to Paradise". Later, Arthur uses the word kaidan ("stairway") to help the Japanese rescuers to locate him (he is lying next to a stairway).
- Arthur tells Takumi that he used a Trail of Bread Crumbs and Takumi compares him to Hansel from Hansel and Gretel. In the end, Joan's favorite book is revealed to be Hansel and Gretel, which is a clue that Takumi was probably Joan's spirit.
- Driven to Suicide:
- Arthur, because his wife is dead and he feels guilty for treating her badly.
- Takumi, because he was demoted at work.
- Earn Your Happy Ending: Arthur was in an Awful Wedded Life, then his wife got a brain tumor, then she died in a car accident, so he was Driven to Suicide. He almost died in the forest. In the end, he is rescued and he finds peace of mind.
- Eiffel Tower Effect: Mount Fuji is showed several times.
- Flashback: Arthur and Joan's life is told in several flashbacks.
- Foregone Conclusion: Arthur tells Takumi that he wants to commit suicide because Joan is dead. So, even when the doctor tells her that she should get better, we know that she is doomed.
- Foreshadowing:
- Takumi suggests to follow a stream downstream. Arthur asks if this is a Japanese survival technique. No, it comes from Man vs. Wild. Then, Takumi sings a Japanese song, which is revealed to be the Japanese version of a song from An American in Paris. This foreshadows the fact that he is not a real Japanese, but the spirit of Joan, a white American woman.
- The Reveal is also foreshadowed when Takumi says things like: "Things are not as they seem here," "This forest is what you call purgatory" or "She is with you. This forest holds her for you."
- Happily Failed Suicide: In the end, Arthur has given up his suicide plan. He has found peace of mind.
- Hollywood Atheist: Arthur is an atheist (he tells Takumi that God is our creation). He treated his woman badly. He was unhappy when his wife was alive. After her death, he is driven to suicide.
- I Gave My Word: Arthur promises to come back to the place where he left Takumi. So, he comes back to the forest, even if he got lost the first time.
- In Medias Res: The story starts when Arthur is going to Japan. His life with Joan is told in flashbacks.
- Lady Drunk: Joan is a classy woman with a drinking problem.
- The Lost Lenore: Joan, Arthur's love interest, is dead. He is driven to suicide because of that.
- Magical Asian: Takumi is a Japanese. He helps Arthur, a white American man, who is a scientist and an atheist, to cope with grief and guilt. He tells him that the spirit of his wife can hear him. Finally Subverted, because, even if Takumi is revealed to be a spirit, he is actually the spirit of Joan, a white American woman. This was foreshadowed by the fact that Takumi's Japanese survival techniques come from Man vs. Wild and that his Japanese song comes from An American in Paris.
- Nature Is Not Nice: Takumi and Arthur are lost in the forest and their life is in danger, because of the lack of food and drink, of the chasms they fall into, of the floods, of the cold...
- Our Ghosts Are Different: Joan's ghost looks like a middle-aged Japanese man. She stays around because she needs to communicate with her husband.
- The Place: The title refers to the forest where Arthur decided to commit suicide.
- Posthumous Character: Joan is dead when the story begins. She is developed through flashbacks.
- The Reveal: Takumi Nakamura is not a real person. He is either the spirit of Arthur's late wife or a figment of his imagination.
- Robbing the Dead: Arthur and Takumi take clothes and other objects from the dead bodies they find, in order to survive in the forest.
- Shout-Out:
- Takumi says that they should follow a stream downstream, according to a survival technique he learned from Man vs. Wild.
- The song sung by Takumi, Rakuen eno kaidan ("Stairway to Paradise") comes from An American in Paris. There is also a poster of that film in Arthur and Joan's house.
- To Hansel and Gretel. Arthur tells Takumi that he used a Trail of Bread Crumbs and Takumi compares him to Hansel. This becomes an important plot point in the end, when Joan's favorite book is revealed to be Hansel and Gretel.
- Surprise Car Crash: Happens to Joan's ambulance.
- Taught by Television: Takumi says that they should follow a stream downstream, according to a survival technique he learned from Man vs. Wild.
- The Topic of Cancer: Joan has a brain tumor.
- Trail of Bread Crumbs: In the forest, some people use ribbons to find their way back. Arthur comes across some of them in the beginning. In the end, when he is looking for Takumi, Arthur uses a ribbon. When the ribbon is too short, he uses paper balls.
- Wild Wilderness: Aokigahara forest is big and wild. It is a popular place to commit suicide, so you encounter many dead bodies. Moreover, you can encounter the spirits of the deceased.
