NSE: Net Sphere Engineer is a single issue sequel to Blame! that was collected into "Blame Academy! and So On".
There seems to be different versions of this chapter with slight changes in dialogue and graphics, most likely the original magazine single print issue came first and later when it was added to the "Blame Academy! and So On" it had dialogue streamlined, graphics slightly changed, and information boxes removed. In one of these versions there is an information box on page 6 that explains some interesting bits of lore.
The setting is described as an "Internet World" where The City was essentially the "hardware" while the Governing Agency was described as the "Operating System". At one time it was a perfect world, where the Governing Agency functioned on basic input-output systems of the megastructure, and completely granted human factor access. However a catastrophe happened (Silicon Life appeared and infected humans damaging their Net Terminal Genes), the world was changed into a dangerous place where Safeguards killed people who accessed The City & Netsphere illegally, now seeing them as foreign threats.
After the main events of the Blame! manga, Killy accessed the Governing Agency (with someone with clean Net Terminal Genes). The Governing Agency and Safeguards seemed to stop functioning altogether. Humans had lost their technological ability that seemed like magic, but in return they received a peaceful world...or so they thought...
Story[]
The story takes place in the future after Killy is successful in his mission. It has been a thousand years since the unspecified master of the city has left, and even the guardians of the city (most likely safeguards) no longer show themselves. Colonies of humans are appearing in the countless layers of floors, but they are unable to proceed past megastructures. People's knowledge of the city carved into the megastructure is beginning to disappear. This story takes place in one such settlement.
In one human colony, with a cultural and outfits very similar to the Electrofishers, gruesome murders have been occurring. Upon the 14th murder, a citizen Kajima who was born with the ability to see from a great distance (complete with HUD display & information in his vision) saw safeguards around the lowest levels of the fungal arrays. Although unmoving safeguard remains are seen every now and then, this safeguard seem to be newly made.
The settlement prefect Hijikaze, who was raised in the capital city in his youth, and was given anti-aging therapy which caused his body to grow larger though he is bedridden. He was the only one in the colony with communication terminal implants. According to colony law such a safeguard must be handed over to the Central Government. Through his communication terminal implants Hijikaze contacted Central and informed them of the situation.
Meanwhile other members of the colony take action. A farmer boy who was searching for a new water source discovers an area with a Structure Conversion Tower, claims the safeguards are coming from it, and summons the village warriors. The warriors wear the same gear as the Electrofishers but they ride horse-like robots. After the farmer boy leads the warriors to the entrance, they leave him behind and tell him they will handle things. The warriors notice a builder, but note that it should leave humans alone. In this area Fairies are seen, which are like those seen in Cave 8 of Toha Heavy Industries. The soldiers then find the Structure Conversion Tower and command their electric technician Sir Denko to get close to it as to cause it to create a Safeguard, which they can bring to the Captial as proof. Denko is hesitant, but is assured that the soldiers can take care of anything produced. As Denko nears and touches the tower it blinks with blue spots, then the spot turns red and a laser evaporates Denko's head. Many red spots appear and several more people are lasered to death. Safeguards appear killing soldiers, and the towers creates more Safeguards that surround the soldiers.
One wounded rider, a female soldier, manages to get back to town having been found by Farmer Boy, she is referred to as "Soldier-san". After she recovers some, she gets up from bed where Farmer Boy has been nearby keeping watch. Together they notice commotion as a stranger comes to the village, he bears the mark of Authority and calls himself a Dismantler. He tells the townsfolk that the Structure Conversion Tower reacts to human presence and creates Safeguard Exterminators, commands the townsfolk not to go near it and to stay in the colony. Soldier-san takes offense to him, as there are hints her culture demands strict obedience to their laws & authority, asking to know about him and where he curtly responds he's a Dismantler and will dismantle the tower. Soldier-San declarers that this floor is under the domain of the Central Government, and he is forbidden to act without authorization. The Dismantler simply expresses surprise that this floor has any sort of government at all, perhaps hinting it is a distant town on the fringes of known human colonies, but says it would explain the nice gear he sees the soldier has. Once again the Dismantler tells them to use the tower, as he has seen countless floors get wiped out from tampering with "relics of the City". He tells the townsfolk to relish the civilization they've built, and not to mess with the "remnants of the Netsphere". Soldier-San still incensed, commands the Dismantler to stop as he is walking away, however she falls to the ground as her wounds bleed. Farmer Boy looks in awe of the Dismantler, impossible for him to believe that anybody came from a different section beyond the megastructures as the megastructures are too thick and there were no known entrances or exits that let you pass through them.
The Dismantler heads to the Tower, he is shown to wear a pendant that acts as a Electric Barrier Generator. As he moves toward the tower, he deactivates the still Safeguard Exterminators. He operates a panel on the tower and it begins to dismantle. Soldier-san confronts him, having followed him, but he informs her that she has alerted the Tower but she doesn't want to listen. The Dismantler fires darts into Soldier-San that paralyzes her armor making it immobile, and he puts his pendant around her and tells her to stay still and be quiet, as Safeguards are created around them. The Dismantler takes out his gun and dispatches of the Safeguards around him. Almost as if in response, the tower creates a massive Safeguard. The Dismantler kicks off a large piece of the tower and accesses an exposed panel to deactivate the tower. Soldier-San finds a way to remove her armor and is now free, begins to take off the pendant but is warned by the Dismantler not to remove it. Defiant she throws the pendant away, however now the giant Safeguard Exterminator fixes its attention on her. The Dismantler fires everything he has into the giant Safeguard Exterminator defeating it before hard can come to her. Although safe, they exchange cold looks toward each other.
From then on, with the Structure Conversion Tower dismantled, no further Safeguard Exterminators appeared.
Years later the Central Government found something similar to a doorway entrance into the Megastructure, but no one was able how to find a way to open it.