The SoulNet was created in the year 19XX as a joint-effort by both Tadashi Hikari and Dr. Wily using a mix of both scientists' expertise, namely network technology and robotics technology. The SoulNet as designed by their creators had the ability to link the souls of humanity allowing them to understand each other and dramatically deepen the trust in each other, thus improving relationships in a major scale. At least as it was originally envisioned by them as neither the SoulNet nor the SoulServer hosting it were finished at this point, but rather only the basic design of both.
In order to finish the SoulNet, Tadashi and Wily had originally planned for their sons to continue their work passing the baton onto the next generation and have them work together to finish it. To ensure that, both Tadashi and Wily split the SoulNet's schematics into two. Tadashi's son Yuichiro, would inherit the records that would come to be known as the Hikari Report, whereas Wily's son Regal would inherit the design.
Secretly Wily feared what the SoulNet could turn to be like as he realized it could be a double-edged sword, a premonition that would unfortunately come true in the future. It is hinted that he added some additional security measures to prevent such an outcome.
As time passed and both scientists parted ways with each other, Tadashi passed away, while Wily was driven by revenge to terminate the network society, the SoulNet's project fell into slumber for years. However Regal would at some point find the SoulNet's design, his legitimate inheritance and use it for his own agenda.
At some point in the the fifth game, Yuichiro would find old files from his father in SciLab's database and learn about the SoulNet. He would then invite Lan and his friends to show them the SoulNet's records, however Dr. Regal would make a move of his own and kidnap Yuichiro in order to secure the other half of the SoulNet in order to complete it.
The Hikari Reports were not on Yuichiro's possession and they had taken the form of Tadashi and Yuichiro's previous dog, Gow who was circulating the net through Vision Bursts. Eventually, Nebula's Darkloids manage to capture to Gow and with it, Dr. Regal begins the long sought goal of finishing the SoulNet, albeit with intentions far more different than originally planned as he wanted to use the SoulNet to turn humans into absolute evil beings.
In order to test this, Regal has his agents move the Nebula Gray from DarkChip production and have it transmitted through microservers in all Electopia. Since the malevolent program's influence did manage to turn people to evil, the experiment was a success and Regal was convinced that once he activates the SoulNet and installs the Nebula Gray, all of humanity will be turned to evil.
The respective teams (depending on the game's version) storm the Dark Chip Factory and attempt to stop Regal's plan. Lan and MegaMan reach the SoulServer's room with the server now finished. Regal activates the SoulNet and installs the Nebula Gray which causes negative feelings to increase within Lan's teammates, however Lan is protected by this as he carries Tadashi's amulet made of MagnoMetal, the only mineral that can block the SoulNet's influence.
Jacking in to the SoulServerComp, MegaMan makes his way to the Nebula Gray where the evil program takes a shape of his own. The young duo fight the Nebula Gray and succeed in defeating it but the Nebula Gray is still operative and attempts to engulf MegaMan in evil power. Lan then connects with MegaMan's soul allowing him to achieve his Hub Form and unleash power strong enough to encapsulate the Nebula Gray. The evil program is too strong to be contained and attempts to possess MegaMan but Colonel.EXE blocks it. With MegaMan's friends linking to his soul, empower him enough for his Mega Buster to blast the Nebula Gray to oblivion, the explosion causing the SoulServer set a chain reaction which is set to destroy the Dark Chip Factory.
A now freed Yuichiro attempts to convince Regal that while Wily fell to evil he never attempted to weaponize the SoulNet, which was proof that Wily still believed in humanity and the project. Regal begins to doubt his evil ways but believes it is too late for him. At that moment (and only fully displayed in Team Colonel), Wily appears in person saying it is not too late for Regal and using his authority and knowledge over the still active SoulNet, sends an electric impulse to Regal's brain which overpowers his MagnoMetal and removes the 10 or so years of his memory allowing him to restart with a clean slate as a law-abiding scientist to be hired for SciLab.
Although the project very much fell apart, it ironically succeeded in reuniting Yuichiro and Regal now as working colleagues with a new vision for the next generation, achieving in a sense what the SoulNet's original creators had intended for so long.
- The basic theory of linking humanity's souls to deepen trust with one another, is in essence the same concept behind the BrotherBand. Although as detailed in some Key Items found in Mega Man Star Force 2, Lan's primary motivation was found in his and MegaMan's ability to unleash miraculous power through their own bond. It is however possible that Lan did in some way include some elements from the SoulNet having experienced it first hand. If true then it would have succeeded in making its creators' original vision to come to fruition, albeit with generations of difference.