Kamui is a harsh landscape, blanketed in a heavy, white snow nearly year-round. Many of the civilizations are hidden between the twin peaks of Ezofuji, at which the Twin Demons Lechku & Nechku are enshrined. The terrain itself is uneven, with snowy land flowing into icy pools where was once flowed freely, making it easy to lose proper footing, slipping and falling all over the place. The island also boasts a thick forest, Yoshpet, from which it is said escape is impossible. However, this is where the tiny Poncles make their home, in a tree stump called Ponc'tan found in an oddly warm and blossoming clearing. Other than this vast forest, the vegetation found throughout Kamui tends to be short and sparse, to due a lack of viable soil in which plants can grow, in addition to a lack of warmth and light to stimulate their growth.
Kamui's inhabitants can be divided into three primary communities. The most prominent of these are the Oina, who view the entire island as their nation and home. These people are wary of outsiders, yet allow them to stay, so long as they do not invade or dwell near their village. Kokari and Onigiri-Sensei are both allowed to make their homes here, but not without precaution. Both are forced to live on the edge of the island, making the second of three communities, away from the rest of the Oina, likely not permitted to enter the village of Wep'keer unaccompanied, if at all. The Poncles dwell far away from these other two, buried deep within the forest of Yoshpet, protected by its hallucination-inducing spores. This tiny race, however, bears a strong connection to the Oina, often growing up alongside one another and becoming close friends. From this, it can be assumed that their relations are good, but that they likely do not try to expand their field of contact.
Given how most civilizations on this island are surrounded by waters, it's safe to assume that the industry that takes the most importance is fishing. The Oina hang the meats in their home, allowing them to dry, to preserve them for use in the winter, when food is more scarce. In addition to that, they keep herds of sheep around both for meat and source of fabric. The homes are largely constructed from the same things that surround them, typically dying or fallen trees and snow. Many mainland homes resemble igloos and sport chimneys to release smoke from the ever-burning fires heating the indoors and its residents. Merchants are found in most of the major residential areas, typically offering the usual wares of Nippon and occasionally providing early access to Divine Instruments.
Kamui has existed since the age of myths when True Orochi destroyed the Celestial Plain which forced the Celestials to board the Ark of Yamato, resulting in the Ark of Yamato genocide and the polluting of Nippon with countless demons. The Ark of Yamato had been permanently frozen in Laochi Lake prior to the events of Ōkami.
Amaterasu first enters Kamui through the Shinshu Field tunnel. There is a fierce, raging blizzard occurring at that moment, and as she seeks shelter inside a nearby hut, Oki notices her and springs to action. Taking his sword and pointing it at her, he circles the fire burning in the center of the hut with her until he is at the door of the hut, then he beckons her to come out and leaves. Amaterasu follows him outside where they battle, and afterwards, Oki admits that she is no ordinary wolf. He also notices Issun, and Issun notices that he has stolen the sacred sword Kutone from its shrine in Wep'keer. The blizzard subsides and Amaterasu is able to venture through the main area of Kamui, and with the help of Yoichi's arrow, revive the Guardian Sapling to remove the cursed zone Kamui had become. In the restored Kamui, she meets Kokari and Ume once again near the sea, along with Onigiri-Sensei and two Oina tribe members, a merchant and Wali. She then proceeds to Wep'keer where, after Samickle displays a hostile reaction to her, she begins to leave until Kai stops her and invites Amaterasu to her house. Kai had recognized Issun's voice as she had known him from a child, and wanted to let him know what had been going on since he left Kamui. Kai's little sister Lika had gone missing, along with the twin demons Lechku & Nechku suddenly having awoken not long before her disappearance. Due to the power of the demons they were warned to stay in their houses and accept no strangers. Oki took Kutone without warning after the village had been attacked, vowing to slay demons until the sword glowed silver to fulfill the ancient legend. During the conversation, the village elder Kemu calls Amaterasu to his house. Upon entering the house, Kemu hears Issun's voice and begins to chase Amaterasu around to hit her, but she is too swift for him and headbutts him instead. He stops and realizes he was sleepwalking, and proceeds to call Amaterasu "Shiranui" and pleads her to help them find Lika in the dangerous forest of Yoshpet as he can smell her scent emanating from there. He explains that Lika is not only a young girl but is also the future and hope of Kamui, as she has acquired spiritual powers past those of himself, and must recite the Volcanic Incantation to cause the Ezofuji mountains to erupt. If this does not happen, the blizzards and the approaching Day of Darkness will cause the temperature in Kamui to plummet below survivable levels and all of its residents will freeze to death. Amaterasu goes past Wep'keer to Laochi Lake, where Tuskle lives, and is told the story of the Ark of Yamato genocide, and lastly is presented with the Oina amulet Sewaprolo, which will enable her to access Yoshpet past the normally impenetrable seal that protects the entrance. Amaterasu enters Yoshpet where Waka greets her at the entrance, but Issun argues with him about his true intentions, and Waka leaves shortly after. Kai is further inside the entrance and offers to guide Amaterasu through the first part of the forest into the area of Ponc'tan, home of all Poncles. When Amaterasu arrives at the area and approaches the tree stump entrance, the Lucky Mallet floats in from above and offers to shrink her down in order to be able to enter the tree stump. She then accepts and is shrunk down and enters Ponc'tan, and visits Ishaku along with other Poncle residents. One of the residents has seen Lika and mentions that Lika went towards the Spirit Gate. However, Ishaku warns Amaterasu to not go near it. Amaterasu returns from Ponc'tan and heads deeper into the forest towards the Spirit Gate, and Issun opens it. Oki appears from behind, noting that Kutone had kept him safe from the pollen that confuses beasts in Yoshpet, and goes through the Spirit Gate, with Amaterasu and Issun following him. They arrive in Kamiki Village 100 years ago and must fight True Orochi to both rescue Lika and fulfill the legend so that they do not change history, and Shiranui appears to save Nagi from a boulder that would have killed him at the end of the battle. Amaterasu and Issun then return to the present with Lika and bring her to the shrine at Laochi Lake to begin the incantation. However, Oki has destroyed the chains on the door of the Wawku Shrine and this has caused a raging blizzard to begin to rush from the gates, unable to be shut. Amaterasu rushes in and navigates the traps of the Wawku Shrine until she gets to a snowy peak; here the demons had trapped the 13th Brush god Itegami and forced his powers to create blizzards. Amaterasu frees him and he then calls together all 13 Brush gods to grant her the Solar Flare reflector, the reflector she used as her previous incarnation, Shiranui. Amaterasu then navigates to the top level of one side of the shrine; there, the silver demon Nechku had been waiting. However, something draws his attention away, and Amateasu and Issun look to see that Shiranui has come from the past to aid them in battle. Amaterasu and Shiranui make quick work of Nechku when Lechku and Oki suddenly crash into the area, locked in fierce combat. Nechku gets up and the two owls begin to synchronize, and Issun admits it's best to back off for the time being. Oki admits no such thing and rushes to attack the owls- however, Shiranui jumps in his way and snarls a warning to him not to do this. He pauses for a moment but swings his sword at Shiranui, and Shiranui dodges, then Oki rushes at the two owls and jumps to land a blow with his sword. At that exact moment, the two owls synchronize completely, and time itself is frozen still. All colors are inverses and even Issun cannot breathe. Oki is trapped in midair and yells curses at the demons, to no avail. One of the owls raises its staff to kill him, but Shiranui overcomes the frozen time and jumps in his place. Shiranui is impaled with the staff and reflexively pulls it out and throws it back at them, stunning them both and leaving them spinning in midair. However, this causes a recoil and Shiranui flies to the edge and nearly falls to certain death, but Amaterasu runs and grabs Shiranui just in time. Oki realizes this is a chance to kill the demons, but a tree branch snaps and begins to fall on Amaterasu and Shiranui. He slices the branch in half, realizing how selfish he has been up to now, and Kutone begins to glow. Shiranui is badly injured and Oki tells Amaterasu to go on ahead, and that he will take care of the demons in the area. Oki appears at the other side of the shrine once Amaterasu gets there, telling her that not long after she left, a "Poncle like Issun" (Ishaku) appeared and Shiranui perked up, and they were able to leave. As Shiranui and Ishaku left through a cut in time with Ishaku's sword, Shiranui displayed a faint smile at the glowing light of Kutone. Ishaku's eyes showed that he was preparing for a grave event- as he knew Shiranui would have to battle True Orochi again, and this would cause Shiranui's demise and set the legend as it was always told. Amaterasu and Oki then team up to defeat Lechku and Neckhu, and they rescue Kamui as Ezofuji finally erupts and brings warmth over the land. Once Kutone is set on its pedestal, returned there by Oki, a brilliant light shoots across Laochi Lake from the sword and the lake is partially melted, and the Ark of Yamato rises from the depths. A rainbow bridge extends from the door of the Ark, and Amaterasu sets foot upon it. As she gets near the door, Issun jumps off and reminisces about their adventures, but tells her he cannot go with her on the Ark and begins to leave. Amaterasu follows him but he slashes at her with his sword to stop, until Waka floats onto the top of the Ark and taunts Issun about knowing he can't enter the Ark, even if he wanted to. Issun takes offense at this and threatens to destroy the Ark just because he can, but is bounced back by a barrier when he tries to enter it. Waka then begins to explain that only those with resolve to fulfill their destiny can enter the Ark and that he never had a ticket for the Ark, and never will. The rainbow bridge begins to fade away and Amaterasu jumps onto the flat door but Issun is too late, and plummets into Laochi Lake. He gives a final prophecy that "It takes two to tango" and shortly after he disappears into the Ark, the door begins to shut. Amaterasu jumps up repeatedly on the door, trying to spot Issun again before it shuts, and Issun silently gazes up at her from below.
- Cherry Bomb 3: In the Divine spring where Cherry Bomb 3 is obtained.
- Tribe of the Moon: In the end directly across the chasm from the entrance of the hidden cave near the path to Wep'keer.
- Cherry Bomb 3: In the Divine spring next to the local Guardian Sapling, which needs to be opened by Cherry Bomb 2. The spring's entrance itself is accessed by a Konohana blossom.
- Sun Fragment: Obtained after the local Bandit spider's defeat.
- #74: Buried outside the Dojo.
- #75: At the end of the bear cave, near the path leading to Wep'keer.
- #76: On the ice waterfall next to the path to Wep'keer.
- #77: Buried near the Mermaid spring (initially hidden by a Devil gate).
- #78: Appears after beating Blockhead Grande in the divine spring.
- #79: Appears after clearing the Devil Gate Trial Cave. As Amaterasu goes up the path to Wep'keer, keep looking over the edge until an alcove with a hard-dig spot and a Clover is in sight. Jump down to the alcove, then down the lower level. The entrance is through a tunnel in the waterfall at the lower level.
- Kamui or kamuy (「カムイ」?) means god in Ainu. In Japanese, it is the pronunciation of 神威 (Kamui or Kamoi), meaning "God's power" or "Divine authority". It is also the name of Cape Kamui, a landmark of Hokkaidō's (the real-life counterpart of Kamui; see the bullet point below), which became the namesake of the seaplane tender/fleet oiler Kamoi of the Imperial Japanese Navy.
- Kamui is an obvious analogue to the real life island and prefecture of Hokkaidō, evident in its location on the map of Nippon, its general climate, inhabiting flora and fauna, its native residents and their culture. Its name is based on the concept of gods and divinity of the Ainu people, and also on the local landmark Cape Kamui.
- The separation between Kamui and the rest of Nippon by what would be the real-life Tsugaru Strait is evident through the fact that the harsh, polar climate with blizzards and snowstorms common throughout the year of the area is not observed at all anywhere else in the country. Several characters' mentions of Kamui being separated from the southern lands by a sea further solidify this fact. This means that the tunnel underneath the observatory at Shinshu Field would be very long as it crosses the strait into the heart of Hokkaidō.
- Throughout the entire region and arc, the player will not find any Wooden Bear treasures. This is thought to be a reference to how the wooden bears carved by the Ainu people, real life inspiration for the people of Kamui, bore no true significance other than to bring revenue from tourists to the region. Ainu culture does not typically allow the depiction of life-forms in most arts.
- In Oki's house, if Power Slash is used on the log he uses for cutting practice, a statue of a falcon will be revealed.
- Near Onigiri-Sensei's Dojo, there are two piles of snow. Power Slash the bigger one and a random snow statue will appear; it will either be Issun x1000, Sakuya, or Amaterasu sitting. Going into the dojo and then returning to the pile of snow will cause it to reset and become covered over again; slashing it three more times will reveal a different statue.
- Near Wali's house, in the snowy section between the frozen streams, there is a large pile of snow. Power Slash it three times and a statue of Amaterasu will appear, similar to the statue in Kamiki Village at the beginning of the game, except larger and made entirely of snow.