Keisuke Ide

Lupin III competes with the Kisugi sisters to steal a triptych of paintings that once belonged to their father, and which hold the key to a long-unsolved mystery. (imdb)

It's summer of 1989 for sixth graders Boco, Joe, and Junichi, their last summer vacation as elementary school students. Brody, son of the commander of the U.S. Forces in Japan, appears before the three of them, stealing their one-year-accumulation of cash. But their conflict is interrupted by attacking monsters. As monsters appear one after another, Gamera, the monster turtle, fights, even though injured, and the boys witness the legend. (imdb)