Ayumu Watanabe’s “Children of the Sea” — the latest feature from Japan’s Studio 4°C, whose films include “Tekkonkinkreet,” “MFKZ,” and “Batman: Gotham Knight” — is adapted from Daisuke Igarashi’s lauded manga, which won the Excellence Prize at the Japan Media Arts Festival. When Ruka was younger, she saw a ghost in the water at the aquarium where her father works. Now she feels drawn toward the aquarium and the two mysterious boys she meets there, Umi and Sora. Like Ruka, the boys — who were raised by dugongs, a type of marine mammal — hear the same strange calls from the sea. Ruka’s dad and the other adults who work at the aquarium are only distantly aware of what the children are experiencing as they become caught up in the mystery of the worldwide disappearance of the oceans' fish. “Children of the Sea” features a score by award-winning composer and longtime Studio Ghibli collaborator Joe Hisaishi, whose credits include “Spirited Away” and “Howl’s Moving Castle.” Appropriate for ages 12 and older.