A Parasite Researcher Fighting with Just One Arm: A Playthrough of Endoparasitic

The protagonist is Shite, a parasite researcher. He was carrying out research at a facility when a dangerous parasite escaped. After being attacked by infected people inside the facility, he too was infested by the parasite. When the game begins, his limbs have already been torn off, and the streamer opens with the joke, "Losing three arms or so is a small price to pay."

After he cauterizes his wounds with an iron lying nearby to stop the bleeding, an announcement plays throughout the facility declaring a containment breach and the abandonment of the facility. According to the streamer, the parasite gives its host tremendous vitality, which is why the protagonist is barely alive, but once the parasite reaches the brain, he will die. This is where syringes become important: they contain a drug his assistant had been researching that slows the parasite's progress. Injecting it extends his life.

The protagonist's research records left in the facility reveal the background of the research. The sample being studied was isolated in a research facility 1 km away, and all research was carried out by remote control. Analysis showed that the sample was a lump of carbon with a structure resembling a bundle of hair, and no unusual substance capable of causing mutations in its surroundings could be identified.

However, when its age was measured using several methods, it turned out to be roughly 4 trillion years old. Given that the universe was born 14 billion years ago, the records speculate that "either the sample has undergone some kind of alteration, or it originates from a universe older than ours." From this, the streamer concludes that the facility was studying a substance that had drifted in from space, and that the main focus of the research was probably the mutations the substance causes in its surroundings.

The first weapon you get is a revolver dropped by a security guard who was already too far gone. Because you can only use one arm in this game, the steps leading up to firing are broken down in detail. You first have to pick up ammunition and load it one round at a time, and if the parasite progresses in the meantime, you also have to give yourself an injection. The streamer accidentally fires the gun while loading it, and enemy voices start to be heard, perhaps in reaction to the noise.

On top of that, you can't move while holding the pistol, so you have to holster it at your hip before moving. The streamer explains the flow of controls: he took down an enemy with four revolver shots, removed the spent casings, loaded new rounds, put the pistol back at his hip, and only then could he move.

Chat logs reveal the makeup and atmosphere of the research team. The three key members are Shite, the lead; Pravi, the assistant; and Lucy, the secretary. When the secretary tells him that the research committee is requesting a meeting about an issue Pravi raised, Shite refuses to let her schedule things on his behalf, saying, "You clearly have no idea how important my research is." The streamer reads the protagonist's arrogance in this, and worries that Pravi and Lucy may not be safe either, just like the security guards who have already turned into monstrosities.

According to Pravi's records, she had prepared 500 doses of a parasite vaccine in case of emergency. At the prototype stage, its effect lasted only a few minutes or so, but she apparently intended to improve it going forward. Shite had called it a waste of time, but Pravi placed the vaccine throughout the facility just in case. In response, Shite's records contain a rant to the effect that Pravi thinks she is always right.

As you progress through the facility, the number of infected grows and your ammunition steadily dwindles. In a scene where he is surrounded by a large number of infected, the streamer has to reload while holding back the parasite with injections, and is driven down to his last round, but manages to make it through.

Shite's experiment logs state that he received 12,000 parasites and 302 guinea pigs, isolated the specimens, and began experimenting. Lucy apparently was not on board. When parasites were exposed to the sample and the mutated parasites were then used to infest guinea pigs, the parasites entered through the skin, and once they reached the brain, the guinea pigs mutated and died shortly afterward. When another guinea pig was exposed directly to the sample for comparison, similarities to the mutation caused by infestation were confirmed. The plans going forward listed continuing until immunity or mutation was confirmed, researching ways to protect against the parasites, and persuading Lucy. The streamer senses that Shite is obsessed with this research and is pushing it forward by force in an attempt to make a name for himself as a researcher.

Later records note that an unusual success case was found in another lab. Despite heavy exposure, that subject developed both immunity and mutation, and far surpassed ordinary humans both physically and mentally. The subject was a former mathematician and was reportedly well known locally as a philanthropist. However, when the subject's family was exposed, most of them died instantly. Shite wrote that there could be no doubt that the sample and the parasites affected by it decide whether a host lives or dies according to their own criteria, and he wondered whether there was any way to uncover those criteria other than mass exposure. The streamer sums this up as a hypothesis that the mutation phenomenon has something like a will and is selecting hosts by some criterion.

During this stretch, you also obtain a new weapon, a shotgun. It can only hold two rounds, but the streamer rates it as more powerful than the revolver with faster follow-up shots, saying its only drawback is how little ammo you can carry.

Lucy's records change the course of the story. She writes that she had a hallucination while handling the parasites. Piedi, the god of light and love, appeared to her in a dream and told her, "That is meant for you." She doesn't understand what it means, but she can't get it out of her head. Shite apparently saw her as "a strange woman."

Lucy had also been acting on her own to find out whether the hallucination was real. One night, she had a drone carry her scarf into the research building and watched through a remote camera as the parasites swarmed over it. Just as she was beginning to feel foolish, thinking that mere parasites couldn't possibly recognize individual humans, the worms started burrowing, and letters reportedly appeared. She incinerated the scarf, but afterward she pored over research materials on the parasites and learned of a success case who had survived the selection and become a god. Ignored by Pravi and treated like a child by Shite, she comes to believe that she must prove her own existence. The streamer takes this as the point where it becomes very likely that Lucy is the mastermind.

Partway through the story, Pravi, the assistant, is killed. After that, the protagonist obtains a crossbow, and his hips end up loaded with weapons: a revolver, a shotgun, a flare gun, and a crossbow. According to the streamer, many of the infected have lost their sight, and many are drawn to gunfire, so the silent crossbow comes in handy. In fact, when he spots an infected that reacts to sound, he quietly slips past it, and in the following situation he gets through by taking enemies down silently with the crossbow.

Near the end, after a scene in which Lucy curses at the protagonist in English, the boss fight begins. The streamer reacts to her lines with, "There's no need to go that far." The boss itself suddenly teleports to attack, also dodges bullets by teleporting, and the revolver has no effect on it. Reasoning that there must be some way to use guns since ammunition has been left lying around, the streamer searches the room and notices that the enemy is connected by cords. When he destroys a core at the end of one of the cords, he finally manages to deal damage.

The strategy is to repeatedly reload between the enemy's attacks and shoot the cores to pieces. However, infected spawn every time a core is destroyed, so the work piles up as you go. After taking out several cores, the streamer says the room has become so full of infected corpses that there's nowhere to put your feet, adding the joke, "Well, I don't have any feet anyway," in reference to the protagonist's condition. He destroys the last remaining core in the upper left, defeats the mutant Lucy sends after him, and the protagonist chases after the fleeing Lucy.

Beyond that, messages such as "oxygen level normal," "tunnel," and "communication system offline" scroll by, and the game ends just like that. The streamer admits that it does feel like it ended abruptly, but says that this is the end of the game's story.

As for interpreting the ending, the streamer limits himself to speculating whether the former mathematician philanthropist and Lucy were chosen by the drifting object because they were people of faith who loved their neighbors. While describing it as a game that leaves many mysteries unresolved, he says he greatly enjoyed the game design of literally controlling everything with only one arm, and closes with, "What do you have to be eating to come up with something like this?"