Move ahead to a pool of lava. Use Waterspout to create a spring of lava. Equip the Fire Tablet and hop onto the spring to ride up to the next level. Continue north and drop into a large pit of lava. There are passages on the left and right that lead to more lava. Both ways will lead to the fortress, but the left passage is recommended as there is a treasure chest there that contains a Crystal. On the right, the Treasure Chest there only has an useless Golden Peach. Nevertheless, look for springs to the north that Amaterasu can use to rise to the fortress above. Approach the doorway to the north and she will be attacked by a Red Ogre and a Blue Ogre. They are not hard to battle. See their links for strategy.
In the next room there is an Imp Merchant, along with a Lockjaw blocking the corridor on the east. Head to the hallway at the west side of the room. At the side of the hallway is a wide room with an Exorcising Arrow at the end. Approach it and Amaterasu will encounter a pair of Poltergeist. Defeat them and take the key back to the Lockjaw to the east. Once through the door, head down the staircase and Amaterasu will meet Tobi, a mysterious spirit in the form of a Prayer Slip that challenges her to a race. To begin the race, headbutt to dash in order to gain speed before running across the floor switch that Tobi is floating over and continue through the doorway that opens. Amaterasu will soon pass through a small gate that rewards her with yen if she makes it there first. A second race is just ahead. For this second race, she needs to make her way over a pit of spikes by jumping on platforms that will fall shortly after she landed on them. If she fails, she can simply try again and this time there will be more panels filling the chasm. Every time Amaterasu starts this race over, more panels fill the chasm to make her trip easier. Again, there's a gate ahead that rewards her with yen when she win the race.
Further ahead, Amaterasu has to use Catwalk to climb a wall and make her way to the next race. This next race is very simple. Just rush forward, jump and make sure she land on solid platforms. However when time runs out, the platforms will open and Amaterasu will fall into a large chasm. Nevertheless, after the race, move forward to the next one. This race is also very simple, but the timing is a bit more demanding. Just dash and don't stop moving forward for a second. She need to keep up movements while jumping and double jumping over the saws to reach the finish. After this race, open the treasure chest in this room, as well as destroy anything destructible in the room in order to be prepared for the next race just ahead. This race is in a passage of spiked wheels. If Amaterasu gets hit by a wheel even once, her chances of winning the race are over, except when she is further ahead of Tobi. Watch the direction the wheels are moving and move through the gap in the wheels just slightly further to that same direction.
Approach the next race. In this race, Amaterasu will have to battle a pack of Headless guardians. Do not farm the Guardians. Use Veil of Mist to slow down time, letting her takes advantage of every second possible. She needs to defeat them quickly to drop the barrier and continue through the finish gate. After that race, she has to make her way through a chasm with narrow pathways and laser-firing statues. Be patient, and make sure to use Power Slash to temporarily stun the statues, as well as Veil of Mist. If Amaterasu takes too much damage, she can heal using the small spring at the beginning of the labyrinth.
After completing the laser labyrinth, Amaterasu will fight a Blue Cyclops before reaching the next race. Luckily, there is water in the room, so Amaterasu can use Waterspout to execute the Floral Finisher of the Blue Cyclops. In the next race, Amaterasu must run through a passage with spiked walls closing in from her sides. Run as fast as possible toward the gate. Use Cherry Bomb on the wall at the end and move out to the roof outside. There, Amaterasu will find an Exorcising Arrow. Backtrack to the Lockjaw just before the race. Through the unlocked door is a room with a chest in the center. Instead of running toward the chest, Amaterasu has to move around the room until she can run toward the chest without crossing any lines of holes, as these holes has hidden spring-loaded bamboo spikes that will damage her Godhood. On the other side of the room is another corridor. The door at the end of the corridor leads to an alcove outside with a large statue of Gekigami. Approach the statue and use Rejuvenation to restore the missing arrow. Gekigami will grant Amaterasu the Thunderstorm Celestial Brush technique. Test out the new brush technique on the Ninestrike-like statue on the side of the door with the lighting emblem on it. Behind the door is another Ninestrike statue. This time the electrocution will power a large spinning mechanism. Quickly run across the spinning platform to reach the other side of the chasm, then move through the next door.Use Thunderstorm to open up the chest in the next hall, then Cherry Bomb the crack in the floor of the circular room beyond. Amaterasu will fall pretty far down before landing in a circular room. Look behind and move through the scroll to find a lightning key at the end of the hall. The key makes the small contraptions around Amaterasu react, which each piece of the contraption will connect with each other and form solid platforms. Take the key to the pathway on the other side of the room that Amaterasu fell into, up to the top of a series of electrical platforms and use the electricity from the key to open the door with a Ninestrike switch. A maze of doors lies ahead, with a lot of items and treasures. To make sure that Amaterasu eventually leaves the maze, observe the map and keep pushing south. If she finds herself heading north, she is going the wrong direction. If Amaterasu is still lost in the maze, or if she wants to obtain all the items in the maze, look at this map. She needs to use a Cherry Bomb to open up the wall at the end. Amaterasu will be back at the room with the two Poltergeist near the antechamber with the Origin Mirror and the Imp Merchant. To the right of the room's entrance is a door with a Ninestrike switch. Use Thunderstorm from the key on it and it will open, revealing a hidden corridor. In the end, there is a Treasure Chest with a Pearl in it.
Once through the maze, return to the antechamber with the Origin Mirror and the Imp Merchant at the beginning. The lightning key will open up the lock at the center of the room. Just past the lock is a statue holding Ninestrike. Use Thunderstorm to strike the sword with the electricity coming from the key on the ceiling, then move through the passage that opens up. Lava fills the next room as Amaterasu enters. Position the camera so that she can strike the four eyeballs in front of her with just one Power Slash. Immediately after, bring out her brush again and spin the camera around to find a fifth eyeball behind her. Strike it to make the lava recede and and continue to the next room. Move forward and use Thunderstorm to strike the Ninestrike switch. A collection of wheels in the area will begin spinning, giving Amaterasu platforms with which to reach the upper levels of the room. Make her way upwards until she finds a wheel that is covered in bamboo spikes. Wait for the wheel to be at a horizontal position, then jump across. She must reach a spinning platform far over head. Use Catwalk on the base of the spiked wheel, and wait for it to be in a vertical position. Climb up the trail, but be quick, and jump onto the spinning platform on the left, then jump onto the edge. Once Amaterasu reaches the top, destroy the wooden bars blocking another electric key. Now, double jump upward to find a small platform. Follow the platforms up the room until she reaches a hidden passage on the left. Run to the end of the passage, as there is a Treasure Chest at the end. Make sure to jump over the trapdoor in the passage, as it will make Amaterasu falls back to the large room with the spiked wheel. After claiming the treasure chest, continues jumping up the small platforms until she finds a Konohana Blossom. Vine toward it, and jump onto the secret passage on the right. Be careful, as the trapdoor in this passage doesn't make Amaterasu fall anywhere, but under the trapdoor is a spiked pit that causes instant death. Remember to jump over it. After claiming the treasure, return to the room with the spiked wheel. Now, with the lightning key, use it to unlock a passage to the far right of the room. Climb up a line of small platforms. Watch for bamboo spikes that shoot up from the floor ahead, and jump through the holes in the rotating platforms of the vertical room. Run toward the door to the next room.
After passing to the next room, grab the lightning key that is to the left of where Amaterasu entered the room. Head into the room next to a laser-firing statue in a corridor ahead. Fight an Executioner guardian and two Headless guardian, then approach the bars. Use Fireburst (if obtained) to light up both torches on the other side of the bars, and lower them. Enter the room.
If Amaterasu hasn't obtained Fireburst yet, then with the lightning key, climb the stairs to a long trail of lightning platforms. Ascend these platforms, then when at the top of the trail, release the lightning key and drop down into the room below. Use Inferno to light up the unlit torch to open the bars at the entrance of the room (these torches would have already been lit if Amaterasu has obtained Fireburst. See above). Pick up the Exorcising Arrow in the room and use a Cherry Bomb to blow open the cracked wall hidden behind a scroll. Just through the blown out wall is a Lockjaw that the Exorcising Arrow will open, letting Amaterasu upstairs to another race with Tobi. Before the race, use the Konohana Blossom on the other end of the pit of poison to Vine back to the main room and grab the lightning key. Head back to the other side of the poison pit with the lightning key and ascend the stairs to a race with Tobi. After starting the race, use Veil of Mist while running across the lightning platforms above the chasm underneath the Blocking Spider. Remember to equip the Golden Lucky Cat to pick up the yen that appears just as the race starts. Jump over the bamboo spikes that come out from the floor and beat Tobi to the finish. Once in the next room, Amaterasu will be attacked by a Red Ogre and a Blue Ogre. Defeat them as she did the first two she fought.
Move through the doors ahead, watch out for bamboo spikes from the floor. There's a Kabegami's statue at the top of the wall ahead, allowing Amaterasu to use Catwalk to reach the top. While standing on the top, draw Catwalk to the other platform, but not straight from the platform Amaterasu is standing on to the other platform. Draw it so the trail of pawprints rise from the bottom of the wall below the platform on the other side to the platform. That way, Amaterasu can climb to the platform and obtain the Treasure Chest without having to worry about the Blocking Spider on her way to the other platform. Use Veil of Mist to get past the Blocking Spider blocking the passage at the bottom of the room, and in the next room Amaterasu will run into an Executioner guardian and some Headless guardians. After defeating the demons, aim the camera at the platform on the left side of the room where Amaterasu entered. Jump to gain a view of the wall behind the platform, then immediately use Cherry Bomb to blast the crack up there open, then use Vine to get Amaterasu onto the platform that is behind the one with the blasted wall (since actually, there are two platforms: the one with the blasted wall is the front, while the one with the Konohana Blossom is the back one). Then, double jump and dash back to the platform at the front, then destroy the line of pots on the small alcove on the left side. Move along the alcove to get to the platform that Tobi is on. This way, Amaterasu can skip the Blockhead behind Tobi (because if Amaterasu climbs to Tobi by the passage outside, then she will have to defeat the Blockhead). Engage in the final race before reaching the top of Oni Island. Despite being the final race, this race is ridiculously easy. Simply use Vine to get across the chasm to the back platform, then rush to the finish. Watch the cutscene, then jump on the lightning platforms on the left. Open the treasure chest on the platform. Move outside, save if necessary, and follow the staircase leading up. At the top of the castle, complete the constellation by filling in the four missing stars and Ninetails will emerge.