Tsuritama/WMG

Haru is actually a Bifauxnen

 * Because those eyelashes.
 * Jossed in episode 8

The Enoshima Dance will turn out to be a summoning dance

 * The Enoshima Dance will summon a huge fish or sea monster, and four people will have to work together to catch it. That's why fishing is so important and why Haru wanted to have a fourth person (he asked Natsuki's dad to go fishing with them) to go fishing with them. The fourth person will be Akira instead.
 * Combined with the "Dragon from the Legend" WMG: the dance will summon the dragon (which is actually an alien).

The thing Haru and Koko are looking for is the dragon from the legend

 * Only it's not actually a dragon, it's an alien, and the goddess who calmed the dragon in the legend was also an alien, one like Haru and Koko. Every hundred years someone has to go and fish up the dragon and calm him down for the next hundred years.