When Rin and Seitaro are exploring the underground tunnel where the mermaids are, Rin says she is cold and so Seitaro gives her his jacket to help keep her warm. And she wears it for the remainder of the game. With all the hostility they've shown each other, it's sweet to see that Seitaro really does care for Rin's well-being.
The good ending is kind of touching and sad. One moment that was kind of touching was Yukio Tsuchida the old man apologizes for putting Rin and Seitaro through all of this and helps them leave with their friends.
Yuka's friends looking for a map in hopes of getting her to a hospital in order to get her strange swollen body examined. This was the original premise until Rin and Seitaro discover the corpses in People Jars.
The "hug" between Seitaro and Rin. Subverted when it turns out that he was possessed and trying get Rin to lower her guard.
The legend of the mermaid was created by the Tsuchida women, who wanted to scare away other women so they wouldn't be kidnapped and eventually murdered. Even terrified of their own family, they still did their best to keep others safe.