Nagi no Asukara is set in a world where long ago, human civilization lived on the ocean floor. However, there were humans who wanted to live above the surface and moved to land, and this created a separation between the humans. The series focuses on four middle school students who live in the ocean named Hikari, Manaka, Chisaki, and Kaname. Because their middle school shut down, they must attend a school on land. During the first episode, Manaka met Tsumugu, one of their new classmates. He's from a family of fishermen and has an interest in the underwater village.
A major focus of episode three has to do with Akari and the guy she's seeing on the surface. Hikari decides to take it upon himself to confront the guy and punch him. After coming up with a plan, Hikari and his friends from the sea go to the surface and watch the fishery cooperative that Hikari discerned he worked at from the logo on the vehicle he saw in episode two. Hikari sees him drive off in a car, and grabs a bike in order to pursue him. Hikari's friends chase after him on foot.
They end up at Tsugumu's house, since Akari's boyfriend had business to attend to there. Hikari runs up and tries to punch the guy, but he is subdued by a net thrown by the older fisherman we've seen with Tsugumu. Akari's boyfriend comes to realize that the guy trying to attack him is Akari's younger brother, and Hikari lets him have it. As a confrontation takes place, Tsugumu comes around a corner.
In this scene, we finally learn what the Ena on the sea people is, and I was right when I guessed back in episode one that it was somehow related to scales on a fish. It's also revealed in this scene that if someone from the sea marries someone from the land and has a child, the child will be born without Ena. Kaname realizes that this is why people from their village are banished if they marry someone from land, and that is also means that there would be fewer descendants. Kaname is absolutely right about that, and Akari even mentions later in the episode that there are only a few single guys left in their village.
We see that Hikari is still feeling rather confused about some things. First, his conflict over Akari being with a guy from the surface; while he wasn't happy with the guy, at least Akari has finally started thinking about herself instead of always trying to replace their deceased mother and putting Hikari first. Hikari also comes to the realization that Tsugumu is actually a pretty good guy.
This episode also sees Manaka struggling with how she feels about Tsugumu, which comes out when Chisaki asks her point-blank if she likes him. Manaka admits that she's not really sure; while he's a nice guy, but she's not sure if she'd want to go out with him or not. Later in the episode, we end up seeing Manaka admitting to Tsumugu that she no longer has the fish on her knee and apologizing for lying to him.
There was also one more interesting reveal in this episode, when Hikari notices that the old fisherman has Ena on his skin. I'm starting to formulate a theory that the old fisherman is Tsugumu's grandfather, which would make Tsugumu a descendant of someone from the sea village. If that's the case, then that would explain why Tsugumu has such a strong interest in the sea village. I'll be very curious to find out whether or not I'm right as I watch more episodes of the series.
One of my favorite scenes in this episode actually takes place very early on, when Hikari and the other three are talking about Akari's situation. When Chisaki says that the guy Akari is with seems like a nice guy, Hikari snaps and tells Chisaki that her taste in men sucks. Kaname gives a sideways glance to Hikari and mutters, "Isn't that the truth?" While I felt bad for Chisaki to hear that from the guy that she likes, it was king of amusing to think about the idea that Hikari is ultimately talking about himself without realizing it. And from this scene, I get the impression that perhaps Kaname might have feelings for Chisaki.
After watching this episode, I realize that I've been sold on Nagi no Asukara, and now this has become a series that I'll be looking forward to watching week after week until it reaches its conclusion. I think I was ultimately sold on the complexity of the relationships between the characters, which really wasn't as evident in the first episode.