This episode begins with the corrupted versions of Warin, Sam, and the Turtle Elder’s daughter confronting Marin and Kanon. They claim that Marin no longer loves Urin and that she wants to kill her, Marin says that’s not possible and she’d never wish for that. So, they say that it’s Kanon and the Turtle Elder’s fault and begin attacking them.
While Kanon and the Turtle Elder are fighting with their enemies, Warin confronts Marin and tells her that her sister is waiting for her, and all she has to do is give into the darkness and all the sorrow and pain will vanish. Marin can tell that Warin’s heart is in terrible pain, so she tries to purify all her friends with her power, but that attempt fails. The Elder tries to give Kanon his fire to defeat the enemies but she refuses saying that the only one who has to be defeated is Senda.
Once Kanon and Marin are able to combine powers they create an affect that is able to purify all of Marin’s friends and the surrounding area. Later, back at Kanon’s house, the girls think that they might have the power to save Urin without killing her, and still be able to defeat Senda. When Kanon’s mother stops by to talk with them they can tell that she’s also being affected by Sedna’s growing powers. So, the girls and the Turtle Elder head off to the sea to find Urin, but before they leave, the Elder tells the girls that if he’s taken over by Senda to please don’t think twice about defeating him.
When the group arrives at the location where Urin was last seen they discover her missing, so Marin suggests that maybe Urin went back to their underwater home. Once there, Marin finds Urin sleeping in her bed, and when Marin makes it to her side, Urin awakens. She tells Marin about a terrible dream she had where Marin befriended the sky dwellers and began to hate her and that she would never come to see her again. Urin says she’s been doing her best to be able to defend herself and she asks if Marin will help her defeat the sky dwellers if they come here. Soon, Urin notices that Kanon and the Turtle Elder are also inside their home and she screams “no”, and unleashes her power blasting a hole in the roof allowing her to flee from the group.
Later, we see the island sea priestess standing near a cliff overlooking the sea where we hear her tell the sea and the sky not to be sad or have fear and that sooner or later the eternal struggle has to end with the light and the darkness finally intertwining with each other.
Marin and her group follow Urin back to the place where Senda was released and they hear Urin having a conversation with Senda. A tearful Urin tells Senda that she thought her sister loved her, and she thought that they would always be together, but Senda tells her that before light can purify the darkness she needs to snatch away the light and leave them in darkness and sorrow. Marin tries to talk Senda into letting Urin go but she just ignores her, and Marin and Kanon attempt to combine powers and purify Urin.
When their combined powers hit Urin, she thinks that this is all the fault of the light, so she uses Kanon’s ring to draw all the power away from both Marin and Kanon. Once Urin has sucked all of their power from them she sends a blast of her own power back at Marin and Kanon.
Urin’s power hits Marin and Kanon and it draws out and shatters both of their orbs of lights, and Marin and Kanon lose their transformations. Then a huge amount of Sedna’s power is released from the seafloor, and Urin tells them that this is the heart of darkness as she sends it towards them, so please give into it. As the power of darkness sinks into each member of the group the Turtle Elder collapses. As the power of darkness continues to sink into Marin’s and Kanon’s bodies they both get weaker, and Marin says this feels like what happened to her at the eclipse.
Now, Kanon and Marin come to understand the true nature of Senda and how she was created, Senda is all the sorrow and pain that the islanders have been throwing into the sea. Sedna is the living combination of all the pain and suffering the island people were unable to share, all the misunderstandings between people, and all the loneliness that the people couldn’t deal with. Kanon knows this for a fact because she can feel Ooshima’s pain and suffering, and she can also feel the pain that her mother couldn’t share with anyone after the death of her father. As, Marin and Kanon are losing awareness, Kanon says that the Turtle Elder had it all wrong, and Marin says that they now have nothing to fear because she now believes that they will be able to save Urin. Well, that’s all for this episode.
Well, only one regular episode of Sea Story left to go, I think that things have just gotten a lot easier for the girls to handle. Throughout the entire series the Turtle Elder has been driving Marin and Kanon forward in an attempt to make them soldiers of light in a battle with their mortal enemy, darkness. It turns out that until now the Turtle Elder and the girls were only operating with half knowledge, I had wondered throughout the series why Sedna couldn’t be defeated for good in the past. The island’s shrine priestess had been trying to drop them hints about the nature of the darkness affecting the island and he refused to listen.
If this had been a typical anime Sedna would have just been a evil creature that needed destroying, but in affect Sedna is the child of every islander who ever went to the little shrine and tossed their loneliness and sorrow into the sea. That’s why Marin felt the same pain from the eclipse when the heart of darkness attacked her, in the previous episode Marin tossed her sorrow into the sea and now it’s returning home to roost. Kanon now understand this because she can feel her mother’s pain, and Ooshima’s suffering. Senda is the creation of everyone who had ever tossed away something to hard to deal with, and now I think both Marin and Kanon understand that Sedna can’t be killed as long as people can’t come to terms with their own emotions.
This understanding now makes Sedna much easier to deal with because you can’t despise or hate Sedna because in the end you’ll only hate and despise yourself. The key to dealing with Sedna is that the girls will have to embrace her and love her breaking the cycle of self-loathing, self-isolation, and come to terms with all of our painful emotions. This is a message that we’ve seen in many popular anime like in Sailor Moon when Usagi says that you can’t kill chaos but you can keep it in the recesses of our hearts, and also in fruits basket when Tohru tells Momiji that we must learn to live with all our painful memories and feelings, we must transcend them because they make us who we are. I think that all the girls need to do is to give Sedna and nice big hug & kiss, and tell her welcome home, you’ve been gone too long.