You know, coming back to it, this part is really weird...

She "knew it"? She knew Ui would go to this random stretch of shoreline when she said she was going home and didn't even realize she was being pulled out to sea by alien influence? Either Ui likes to do emo staring out to sea at this exact spot like Kuroki Tomoko during that one chapter that we never hear about, or this is some major plot contrivance.