The police investigate an empty zoo, wherein every cage has been ripped open from the inside. There, they discover the nightshift zookeeper, clutching feathers in his hand, utters with his last breath, "I saw a bird!" Meanwhile, Jun, Yuriko, and Ippei investigate the appearance of a strange, medieval sailing ship. Finding the ship's log, they encounter a small, finch-like bird. Suddenly, the ship begins to fall apart and sink into the bay, and the bird gravitates to Saburo, a young orphan boy. As Saburo sleeps, the bird he names "Kuro," flies out at night to feed....With Yuriko's help, Professor Ichinotani identifies the creature as Largueus, a giant bird thought extinct before the Third Ice Age.
ある晩、動物園から動物が一頭残らずいなくなる事件が発生。「鳥を見た」と謎の言葉を残す飼育員。同じ頃、漁村に謎の船が漂着し、村の少年・三郎は船から飛んできた小鳥と交流を深めていく…。
