The Beginning of the End (OVA 1)
Two angels; Chihaya and Kagetsuya are sent from Eden by Archangel Michael to Earth to further study Earthian behaviour. Despite an incident in Hong Kong where Chihaya exposed his wings to someone, both he and his partner are given a new assignment to study human activity in Shinjuku. There Chihaya befriends a young woman who is more than what she seemed.
The woman who is named Takako is actually a gynoid, created for the purpose of further study by Dr. Ashino, so that he can try and ascend humanity to the level to God. Takako escaped from a facility called The House where they were about to implant a fail safe system into her which would reduce her experience to human emotions and therefore not bring her blood to a boiling point, where her heart could self-destruct and take out a large area of the city and killing many people. After a run in with Dr. Ashino's other android creation; K-001, both Chihaya and Kagetsuya exposed their wings to the gynoid, before finding help from a doctor who it turns out was helping to hide an android from Dr. Ashino; who helped Takako to escape. That android was Taki, the one who Chihaya exposed his wings to back in Hong Kong.
K-001 soon arrives at the doctor's clinic and kidnaps Chihaya and says that he would only be released if Takako gives herself up. Soon both she and Kagetsuya go to The House to rescue Chihaya, of whom Dr. Ashino has taken an interest in that would help him to set the stage for events that take place in the later OVA's.
Fallen Angel (OVA 2)
Of the four OVAs in the series, Fallen Angel is the only one that does not relate to the events of the first.
Chihaya and Kagetsuya are staying in France for their current assignment, and lately Chihaya has been having some disturbing nightmares. As Kagetsuya tries to console his partner over breakfast, Aya and Miyagi show up on vacation, and decide to stay in France for a short while.
Chihaya and Kagetsuya's mission is to locate the exiled angel named Sapphire, who has been hiding on Earth ever since his wings became black with cancer. Chihaya discovers Sapphire's whereabouts, and, learning about the former High Angel's predicament with some shady dealings, he lets himself become involved, much to the dismay of Kagetsuya, who knows that every time something bad goes down with the Earthian, it is always Chihaya who suffers.
The partners struggle to help Sapphire while keeping everything a secret from their guests, but Chihaya's exceedingly strange behavior has not been lost on Aya, and she begins to make some deductions of her own. Both she and Miyagi are well aware of the fact that Sapphire's disappearance has not been taken lightly back in Eden, and as it is, any fallen angels are considered to be a huge disgrace.
In the midst of all this, Chihaya is also hiding a secret of his own; one that has to do with the frightening dreams he has been having. His fears are eating away at his heart, and he worries that what happened to Sapphire might be the same thing that caused the abnormal color in his wings and hair.
Angelic Destroyer (OVA 3)
Picking up where the 1st OVA left off, Chihaya and Kagetsuya are trying to infiltrate Dr. Ashino's lab in order to rescue two black angel children who are being held for interrogation by the mad doctor. The pair split up to search for the hostages, and while wandering through the corridors, Chihaya discovers, locked away in a side room, a black-winged angel like himself, attached to wires extending from the walls.
The angel's name is Messiah, and Chihaya, desperate to get the dormant figure's attention, exposes his wings at the window of the room. Messiah's memory chip, still in the process of being encrypted, takes in the image of Chihaya's transformation and fills Messiah's mind with strange emotions. He is compelled to approach the angel on the other side of the glass window, but cannot get out of the locked room.
An alarm begins to sound, and Chihaya and Kagetsuya meet up again, Kagetsuya carrying the two children. They are forced to evacuate the lab immediately, as it is about to explode. Elvira, the mother of the children, pulls up in her car and help them get away. Chihaya is deeply troubled that he was unable to save the black-winged angel.
One morning, while watching the news, Chihaya discovers that Doctor Ashino has arrived in the city accompanied by a strange man in a trenchcoat. Chihaya immediately recognizes the man as Messiah. Ashino has been having dealings with the military, and was commissioned into creating the ultimate weapon of destruction: Messiah. However, he is not in it just for the money. Troubled by the fact that Taki abandoned him, Ashino is plotting revenge against the entire world, who stood by despite his suffering.
Final Battle (OVA 4)
Chihaya is reluctant to accept Messiah's disappearance, and no matter how Kagetsuya tries to comfort him, he can only ever think of the android whose wings were like his. Messiah, in the meanwhile, is making his living carrying out errands for a club of drug dealers. He feels accepted by these people, who are appreciative of his physical strength, but longs to find Chihaya again.
Using his connection to the world's computer database, Messiah searches for his friend. Chihaya, also online, discovers Messiah's call, and rushes to meet him in the sky. However, Ashino has also been tracking Messiah, and he sends in men to capture the runaway android.
Ultimately, Messiah needs to choose between staying with Chihaya and learning more about the emotions that confuse him, or give up his freedom in exchange for the assurance of Chihaya's safety, and become the weapon of destruction he was intended to be.
