The video on Ushio’s unlocked phone shows both the original Ushio and her Shadow delivering a joint message to Shinpei. The original assures him her Shadow isn’t evil like the others, but an ally, then proceeds to tell the story of how she ended up dying, and why that’s not the end of her story, because ultimately she is her Shadow and her Shadow is her.
It started with Shiori telling Ushio about seeing her own Shadow and asking her for help, since no one else will listen to her. Then, while Ushio and Mio were cleaning up the beach, there was a flash from above and just like that there was a second Ushio, who runs away before she can learn anything more.
Ushio comes home for a bath to find the other Ushio is already in the tub; she went home because it’s her home, same as Ushio’s. Once she determines that this other Ushio isn’t a threat, the two join forces to seek out Shiori’s Shadow on Mt. Takanosu, the locaiton of Sou’s family’s old clinic, believed by most of the island to now be haunted. It is haunted, but not by ghosts…by a monster.
A Shadow in its black goo form copies Ushio’s copy and tries to kill her, but Shadow Ushio figures out on accident that the copy’s weakness is not its body, but its shadow, and that she can use her own body—like her hair—as a weapon to slice through that Shadow. She can also repair her physical body, and tells Ushio that the instinct to kill her original “fills her brain”, even though she has no intention of doing so.
The two Ushios return to the beach to record a message for Shinpei, and after the present-day Shadow Ushio watches it with Shinpei and Sou, she suddenly regains her memories and knowledge of her power. She uses that power and her phone to “transport” the three of them into a recording of the tragic events of July 21st on the private beach where original Ushio breathed her last.
Original Ushio had Shadow Ushio turn into a seashell necklace and wore her, so that when Shiori was washed out to sea, not one but two Ushios were there to rescue her. However, under those waves Shadow Shiori kills her original and drowns the original Ushio—the one Sou was unable to revive and ended up being cremated.
Struck by her original’s sacrifice for both Shiori’s sake and her own, Shadow Ushio vowed to help Shinpei wipe out the Shadows when he returned to the island. As Sou and Shinpei weep over what they witnessed, Shadow Shiori suddenly grabs Shin’s arm and transforms into Haine, who promises he won’t escape her next time.
Shadow Ushio switches of the recording so she, Shin and Sou are back in the present, but Shin now has a sinister black mark on his arm where Haine touched him, proving that it wasn’t just part of the recording, and that Haine is apparently capable of transcending time and space like he can.
That adds an extra layer of difficulty and dread to Shinpei’s task, but the recordings he and Sou watched proved one thing: Shadow Ushio is indeed their ally, and they need all the allies they can get against an increasingly menacing enemy.