Akira is waiting for Miki outside of school. He says he was reading in the library, to which Miki remarks on how he should pick up a sport because he has the build for it. Akira says he doesn't think he has the right personality for athletics because he is not aggressive enough, and Miki makes fun of him, recalling how much of a crybaby he was in elementary school. It's revealed that Miki's and Akira's dads are good friends.
Dosuroku and two members of his gang show up to hassle them, mocking them for walking home together like a couple. Akira tries to ignore them and suggests Miki do the same. She gets annoyed at him for not fighting back and calls him a crybaby again, then starts to hurl insults back at the gang. Akira tries to get her to stop, but she won't, and Dosuroku and co. are getting pretty angry. Eventually she mentions her nickname "Miki the Hands"* and slaps the two goons, but when she tries to slap Dosuroku, he grabs her and shoves her against the wall while she calls for Akira's help.*Translated as "Slapping Miki" in the Classic Collection, but "Miki the Hands" is the more widely accepted title by English-speaking fans.
Akira tries to defuse the situation, explaining that he's walking home with her because he's staying with her family, but this just leads to some sexual comments about Miki. Miki tells Akira to stop talking to them and fight, but the scene is interrupted by the arrival of Ryou, who ignores what's happening and tells Akira to come with him. Akira gestures towards Dosuroku, who is still itching for a fight, and tells Ryou that they're kind of in the middle of something, so Ryou pulls out a sawed-off hunting rifle. Dosuroku tries to call him out for bluffing, but it turns out the gun actually is loaded, and Ryou fires a few shots at their feet until all three delinquents run away. Akira runs off with Ryou, leaving a bewildered Miki behind.
Akira questions Ryou, and Ryou tells him that he believes his life is in danger, but won't elaborate on the threat. He leads Akira to a car, and Akira exclaims that he is under eighteen* and therefore too young to drive, but Ryou says he altered his father's license and insists that it will be fine.* Few of the character's ages are confirmed, but we can assume that since they are in high school and in the same class, Akira and Ryou are between 15 and 17, and most interpretations place them at 16. Miki is either the same age or one year behind them (as she is in Saga). In Gekiman, Miko is said to be 16, but her classmates are said to be 17, so she is either the same age or one year ahead.
Akira comments that Ryou is acting strange and reckless, but Ryou blows him off. Akira mentions that his dad "took [a] job overseas [a month ago], and [his] whole family* went with him". Because of this, he moved in with the Makimuras and had to switch schools, and has not seen Ryou since. He says that they are best friends, but Ryou has changed a lot over the past month, and continues rambling until he trails off, realizing that Ryou is not responding. After a moment of silence, Ryou suddenly exclaims that his father is dead, making him the last surviving member of his family. Akira becomes distraught, saying that Dr. Asuka looked fine the last time he saw him, and Ryou reveals that he committed suicide by pouring gasoline on himself and setting himself on fire.* Akira never mentions having siblings or other immediate family besides his parents, and the fate of his parents is never addressed.
Ryou continues, saying that Dr. Asuka's body "was twice as heavy as when he was alive", weighing almost 300 pounds despite his thin frame. He then says that his father left him a "dreadful inheritance", and says he wants Akira to share it with him. Akira seems frightened and uncertain as they pull up to the Asuka manor.
Outside of the gate, Ryou stops and faces Akira, saying that he is his best friend and the only person he can trust, begging him to understand. Akira says that, despite his fear, he's "with him to hell and back", the narrative remarking on the irony of those words.
Ryou reminds Akira that his dad was a famous archeologist. Akira says he assumed his life would be boring and comments on a photo of him with "some hot foreign chick", which turns out to be Ryou's mom*, much to Akira's embarrassment. To change the subject, he asks about the inheritance, and Ryou leads him down a hallway towards his father's lab. Ryou explains that his father was studying Mayan ruins** when he fell into a hole and uncovered something strange.* This reveals that Ryou is of mixed race; Nagai has confirmed multiple times that he is half Japanese and half (white) American. Additionally, since Ryou says that Dr. Asuka was his last living family, this means that his mother is dead, too.
They enter a dark room, but the demon mask is clearly visible. Akira screams and tries to run away, but Ryou points out that it's not real. Akira says it looks like the Devil, and asks if it's an ancient artifact. Ryou confirms this, but says it is much older than humanity, and was created by demons, who ruled the earth before humans arrived. Akira calls him crazy, but Ryou continues that the sculpture is meant to be worn, and will broadcast a series of visuals to the wearer, showing the history of demons.
Akira tries again to flee, calling Ryou crazy again, but Ryou pulls the best friend card and Akira reluctantly agrees to stay. Ryou eventually persuades / guilts Akira into putting on the mask. Akira sees the scene unfold in front of him as if he were there: dinosaurs, an erupting volcano, and most importantly, demons. It's a gruesome scene, as the demons exist in constant fighting and bloodshed. "Weakness… meant death […] a history of violence! Blood calling for blood! Slaughter calling for slaughter!" as Ryou says.
Ryou explains that demons possess the ability to merge with other matter to enhance their own power, and over thousands of years they became "grotesque monsters". He compares this to humanity developing more powerful weapons over time, and says that the era of demons came to an end with the ice age. Akira expresses relief that all the demons died during the ice age, but Ryou corrects him (with dry sarcasm) that his father theorized that the demons were still out there, bringing up various creatures from folklore as examples of possible demons throughout history. Akira admits that this makes sense.
Ryou asks if Akira's heard of Dante's Divine Comedy, which he has not, so Ryou summarizes that Dante wrote a guidebook to heaven, hell, and purgatory, and in it he describes the demons being frozen in the lowest level of hell. Among them is their lord, Lucifer, who is said to have bat wings and three heads*. Ryou suggests that the demons did not die in the ice, but rather have been hibernating, and have been slowly emerging overtime as the ice melts, inspiring those myths. He continues that most are likely still trapped because there are no fossils to indicate that they died.* Although at this point in the story Nagai had not planned for Ryou to be Satan, this functions as a bait-and-switch for later, as this description fits Zenon and not Satan. Additionally, in the Divine Comedy, the ice that traps Lucifer is composed of his own tears and saliva.
Ryou says that in order to prove the existence of demons and conduct further research on them, his father willingly merged with one, but that when the demon began to overtake him, he lit himself on fire. Ryou gets emotional as he describes this, saying that in the end his father only begged for more gasoline, and that Ryou didn't understand what was happening until he read his suicide note. Akira tries to console him, saying that it's okay if he needs time to process it, but Ryou, getting ahold of himself, laughs dryly and explains that time "is exactly what [they] don't have."
Ryou says that a demon and a human cannot simply merge under normal circumstances, and that he will explain more later. He says that the demons are already awake and planning to take back the earth by destroying humanity. Akira points out that humanity has strong militaries and nuclear weapons, so they have a fighting chance, but Ryou counters that demons' bodies are their weapons, and that they've been studying humanity to find it's weaknesses with the intent to wage war. From the demons' perspective, humans have infested their land.
Ryou goes on to say that humans refuse to believe they even exist, which has enabled them to slip in undetected. He says that "by the time humans admit demons are real," they'll have already won. He brings up his inheritance again, saying that it is the only chance humans have against demons. Akira, mind made up, confirms that he's still in. Ryou seems hesitant but says that they'll do it tomorrow. As they get back in Ryou's car, Akira asks why they're waiting, and Ryou admits that it's because he himself is scared.
As they're driving, a demon shows up and blocks the road, shattering the car's windshield with a sonic screech. Ryou turns around and tries to escape, but more demons descend upon the car. Texsch lands on the roof and tries to get her tentacles into the car. Ryou hands Akira his gun and tells him to shoot at it, but Akira says he doesn't know how. One of Texsch's tentacles gets inside, but Akira is too freaked out to shoot, and it wraps around his neck. Ryou whips out a knife and manages to sever the tentacle, then grabs the gun and shoots her between the eyes.
They make it back to the manor and Ryou crashes his car through the wall. He makes sure Akira is okay, then makes a break for it. Akira, trying to be polite, asks if they should take their shoes off, and Ryou scolds him for his poor prioritization. Ryou leads Akira through his house to the room where the "inheritance" is, with Texsch still in pursuit of them. He says that Akira doesn't have to come, even though staying behind means dying, because death might be a better fate than what awaits them, but Akira, scared of Texsch, says he doesn't want to die and begs Ryou take him to the room.
They run through the house, Texsch close behind them, and turn down a hallway. Ryou makes a poorly timed joke about it being a dead-end, but quickly reveals a hidden door. Once inside, Ryou opens another secret door, saying that it only opens from one side, and once they enter they won't be able to come back out, but with Texsch climbing through the wall again, they have no choice but to jump in.
They walk along a fortified corridor with the inheritance at the end of it. Ryou laments that he wanted to give Akira one more day to enjoy his life. Akira asks why the demons are attacking them, and Ryou says it's because his father uncovered the demons' plot while he was merged.
They arrive at the room, and Akira tells Ryou that he's pieced together what the "inheritance" is, saying that from what Ryou has said, there's only one logical way to stop the demons. Ryou gets emotional again that Akira had figured it out but was still willing to go along with it, and confirms that in order to win the fight against the demons, they must become demons themselves. He elaborates that this would mean throwing away their humanity completely, including all sense of emotion, and continues crying as he apologizes to Akira for "[putting] him into a position where he can't refuse*". Akira insists that he's not scared, and would rather become demons together than "watch [Ryou] suffer alone."* Note that by this point Ryou has, in fact, tried to give Akira several outs, and every time Akira has chosen to go with him.
Akira asks Ryou why Dr. Asuka had to kill himself, and if they're going to have to do the same. Before answering, Ryou lights up a joint, much to Akira's confusion. As he smokes, he explains that after his father's fusion, there was no clear evidence that anything had changed, because demons possess the ability to shapeshift. Ryou remarks that "his true form was probably grotesque," but he never revealed it to Ryou because "he didn't want [him] to see it."
Ryou then goes on to explain that when a demon fuses with another living thing, it is a merge of consciousnesses as well. He explains that, although his face looked the same, his father began exhibiting irrationally violent behavior, such as ripping apart Ryou's pet canary and decapitating Ryou's dog, John. When Ryou confronted him about this, he was covered in John's blood and saying disturbing things. Two weeks passed, and he tried to kill Ryou in his sleep, but Ryou was able to stop him, and he regained his clarity long enough to lock himself in his room for three days before ultimately comitting suicide, unable to bear the thought of almost killing his son. He wrote in his note that he was unable to fight the demon's bloodlust any longer, and wished to die "while his heart was still human".
Dr. Asuka then theorized that there must be people who would be able to merge with a demon without losing their human souls. He wrote that "they must possess an iron will, strong enough to contain the demon," "retain a pure, unspoiled heart," and have "a powerful sense of right and wrong". Ryou points to Akira and declares that he is the type of person his father was describing. Akira denies this, but Ryou insists, saying that he believes in him, which is enough to convince Akira.
Though Akira is still nervous, and asks what happens if the demon wins. Ryou replies frankly: if either of their possessions fail, they will have to die. Akira says he understands, and draws an analogy between the current situation and Ryou being Enma leading him into hell*. They clasp hands and share a moment of intense silence (with some dramatic tears) before Akira enthusiastically calls for Ryou to "open the gates of hell". Ryou flings open the door to reveal the Sabbath inside.* Enma is the Japanese name of Yama, the Buddist god of hell. In the English translation, this reference is changed to Charon and the River Styx from Greek Mythology, likely so that westerners would be more likely to get the allusion.