The movie itself says the character is "unknown", but the Link Navigator has it "Otoshigo". Taking the face meanings of the three kanji, it seems to mean something like "Fallen Prodigy", though those same kanji are mainly used in Buddhist writings.
081 +22:28 Nagai Yorito ----- Secondary - VIDDLER / GAMEVEE (Archives: None)
082 +23:00 Unknown ---------- Movie ----- VIDDLER / GAMEVEE (Archives: 95)
The Denizen of the Deep
Otoshigo is one of the ancient entities that escaped into the ocean depths. Though it wailed after its companion, who sought shelter deep underground, its cries went unanswered. The grief-stricken wails of Otoshigo shake the seas, bringing disaster and misfortune to any who wander in its path.