First Reploid

"The first Reploid" is an unseen character from the Mega Man X series mentioned in The Journal of Dr. Cain. It was the first Reploid created by Dr. Cain, which he built with X's help after studying Dr. Light's notes and finished on November 22, 21XX.

Although Cain could not completely understand how all of Dr. Light's systems works, he was able to make some minor modifications and the Reploid seems to be functioning perfectly. His strength and intelligence seem limitless and he is fully able to make his own decisions, and even had an argument with Cain, which he found intriguing. Some time later Reploids began to be mass produced.

Mega Man (Archie Comics)
Dr. Cain's first Reploid had a brief appearance in Mega Man #34 as part of the comic adapdation from the Journal of Dr. Cain.

Rockman X The Novel: Irregulars Report
The first Reploid was created by Dr. Cain 35 years after he found X. 20 years after Dr. Cain found Dr. Light's Laboratory and studied Light's notes, he had understood about 80% of X's structure, and filled the functions he could not grasp with his own research. 10 years later, Cain decided to announce his plan to start the development of robots that can think by themselves, and about 5 years after his announcement he developed his first robot to showcase to the world. Cain named him Alpha (アルファ), based on how X meant an unknown number. Alpha was more human than he expected and overwhelmed people across the world, and human-like robots, which became known as Reploids, were accepted as partners of a new age, marking the beginning of competitions between scientists across the world to develop Reploids.

10 years since Cain showcased Alpha to the world, Cain decided to finally undo X's sealing and awaken him, keeping his origin a secret and telling X that the one who made him was a friend that passed away. And thus Cain's life with Alpha and X, and between humans and Reploids, began, the two Reploids becoming like foster brothers and sons to Cain.

Another 10 years have passed since X's awakening. After spending time with X, Cain thinks he should have awakened him sooner, being surprised to how unique and human-like X was, being self-aware and able to converse like a human. Cain felt ashamed at having prided himself in saying that Alpha was the culmination of his work, considering the way he covered the "black boxes" clumsy compared to Light's work and noticing that X's heart was complete before he even began to accumulate experience. During the years, Cain continued to research X and applied his traits to Reploids, including Alpha, who he has been constantly updating while making him be the center stage. Cain kept on making updates until Reploids that could hold natural conversations became commonplace; and that's when, finally, Reploids that had a bug on their thought circuits, called "Mavericks", began to appear. The Maverick Hunters were formed to carry out suppression by themselves, and the development of battle Reploids progressed at an accelerated pace. Cain also continued developing new types of Reploids and finally created what he considered his masterpiece, "Sigma", who climbed to the position of Chief Executive of the Maverick Hunters in less than a year.

On a rainy day, an incident happened. Alpha had gone out with an unit led by Sigma to assist in subduing a mysterious red Maverick, but since Alpha had no combat abilities, his mission was to gather data and report back to Cain. When the red Maverick was subjugated and the unit returned, Cain went to the Hunter Base alongside X. Cain had to analyze the red Maverick, but first he went to the maintenance room to repair the Reploids that participated in the mission. He started with Alpha, who had risked his life to create an opening for Sigma. Suddenly, Cain is hit and thrown a long distance and is disoriented until a beam of light passes near him. When he noticed what was happening, he could not believe it. The kind Alpha was aiming a portable gun to Cain and was saying that he would kill him. Everyone in the room was in panic and both Cain and X tried to talk with Alpha, but Alpha was troubled, appearing to be filled with anger or fear, and would not listen to them.

Alpha stated that he was a piece of decoration since his creation, asking what would be of him after his role as the first Reploid had ended, and felt inferior to Sigma, who Cain considered his masterpiece. Cain told Alpha that he is part of the family, regardless of his role as the first Reploid, and there is no inferiority or superiority between him and Sigma. Alpha doesn't believe Cain, and X tries to talk with him, asking what he wished. Alpha said that he wanted freedom, something he could not have while Cain was alive, so he had to kill him to be able to live his own life. X told him they could not do it, as Reploids must protect humans. Alpha became more violent and told X to not get in the way, preparing to attack Cain, but X instinctively shot him down with the X-Buster to save Cain.

Dr. Cain could not understand why Alpha behaved like he did, but he knows his program was not altered as he placed special protections on his programming and no alteration was made in the last months. Both lamented Alpha's loss due to him becoming a Maverick, and Cain tried to comfort X by saying that he had saved his life, worrying that X may blame himself for what he did. As a result of the incident, X began working full-scale as a low rank Maverick Hunter.

Trivia

 * In some sources, such as one of the Rockman X6 guidebooks and Marvel vs. Capcom: Infinite, Sigma is said to be the first Reploid created by Dr. Cain.