|Allies||Aya Drevis, Snowball, Subjects, Maria|
Dio, also known as the "Blonde Boy" (金髪の少年 Kinpatsu no Shonen), is a seemingly undead boy that Aya encounters in the mansion. His intentions seem to be good when she first meets him offering to help her by showing her the way, but Aya is shocked when she realizes half his face has been horribly burned and runs away, terrified.
Later on, after she was almost choked by a subject, Aya faints and Dio takes her out of the room. After she wakes up, he tries to convince her to escape from the mansion, which she refuses. After that, Maria appears and throws knives at him.
He is not seen again until one of the endings. After Maria fails to kill Aya's father by throwing knives at him multiple times before he can kill Aya, the mad father gets up and tries to end them both. Dio saves them by killing the father personally just in the nick of time.
Later in the story, before Aya and Maria are preparing to leave, Dio says Aya has no need to thank him and reveals it was her mother who had sent him to make sure she wasn't hurt and says he had no intention to be injured or to have scared her earlier. He tells Aya to not be sad, because her mother is watching over her and if she is sad, so will her mother be.
Dio continues to explain he must now set fire to the mansion to get rid of any traces of her father to prevent what happened repeating itself, and asks Aya to remember everyone that died there and sacrifices made since their existence would be forgotten. Aya agrees, and as the mansion begins to burn Dio kisses Aya on the forehead and says "Goodbye Aya. May you be smiled upon." This is a charm previously shown to also be given to Aya earlier by her mother before she died. It is a reference to this.
Aya and Maria leave, and the mansion and Dio are seemingly consumed by the flames along with the other reanimated corpses in the mansion.
In version 2.00, it is revealed that after Aya passed out from the shock of her father dying, Dio and Maria spoke briefly, during which Maria commented that Dio seems more alive than the other corpses, apologized for throwing knives at him earlier, and expressed her regret that she can't stop Dio from disappearing when the curse fades. Dio responds that it's his fate to disappear, and asks Maria to take care of Aya, as that is her fate and Monika's wish.
Dio leaves and wanders the house, where he meets Ogre and sees his twisted nature, realizing that he isn't human. Ogre tells him that he enjoys watching the actions of lunatics, but that good people like Dio are also necessary to let the lunatics of the world flourish. It is also revealed that Ogre saved Dio's life after he was attacked by Maria, by giving him medicine. Ogre then disappears. Dio also speaks to the corpse of an old servant, who suggests that Dio came to the Drevis household as a servant too, then accuses Monika of being sharp to the extent of seemingly reading minds, and suggests that she has deceived and brainwashed Alfred and possibly Dio himself. Dio refuses to think ill of her, insisting that her feelings for her daughter were real.
After Aya wakes up, Dio warns Maria to be careful of Ogre, saying that he could endanger Aya.
After setting fire to the mansion and bidding farewell to Aya and Maria, it is revealed that Dio actually left the mansion rather than staying to be consumed by the flames. He comments that he is returning to a lonely life, and expresses his gratitude to Monika for saving him, although he still wonders why she did it. As he is about to depart, one of the mansion's dolls appears and asks why he chose not to leave with Maria and Aya. Dio reveals that he is actually alive, rather than a reanimated corpse; and answers that he is worried about how they would react if they knew, and that he chooses to walk a separate path so as not to drag them down. The doll suggests that Dio may reunite with Aya and Maria someday if they are connected by fate, and asks what Dio will do if he finds that Aya has followed the same path as her father. Dio expresses disbelief at the notion, stating that Aya should understand the subjects' pain better than anyone; but says that he would try his best to stop her if that turned out to be the case. Dio then departs the mansion as the doll goes to sleep with the fading of the curse.
Dio is not his real name. His name is never mentioned in the game itself, but many of the niconico fans began calling him Dio after a character in Jojo's Bizarre Adventure. The name Dio stuck and was later added to his bio in the endgame material. His real name, however, still remains a mystery.
Dio has tousled blonde hair that covers a small portion of the right side of his face, swept to the right in order to not obstruct his view. He has bandages bounded around his head that conceals his right eye. Dio has hazel colored eyes and is missing one that was taken away by the Doctor at a young age. His attire consists of a white collared shirt and brown pants, with straps over his shoulders. Dio has a rather lanky build, though he is stronger than he looks. His expression usually remains stoic throughout the game. It could be said he is possibly around the same age of Aya who is eleven.
What you can take from his short appearance in the game, he is a quiet and a slightly stoic young man. He knows what he has to do and stays focused. He is thankful for Aya's help and wants to be remembered. He seems more mature for his age (his age being that of a young teenager, possibly 13/14), maybe due to what he has experienced since coming to work for the Drevis family.