New World Lovetopia Memento (prequel)

Once upon a time there was a "great hole" between the other world and the human world, through which various otherworldly creatures flowed into the human world. The one-way "great hole" kept the otherworldly creatures in the human world, where they began to coexist with humans. The tribe of angels, unable to return to their original world, keeps searching for the "great hole to return to", but they reach a certain young man…?