The story of Steins;Gate begins with Rintaro Okabe and Mayuri Shiina attending Nakabachi's press conference about time travelling. His presentation angers Rintaro, who accuses him of plagiarizing John Titor's research. He loses his temper and yells at Rintaro, ordering him to stop. He is not seen again after that.
At the very end of the plot, Okabe, along with Suzuha Amane, time travels back to the day of the conference to prevent Kurisu's death. It is revealed that his real name was Shouichi Makise and that he is Kurisu's father. He attempted to murder her to steal her paper on time travel. Okabe tries to stop him, but unintentionally stabs Kurisu himself.
Rintaro then has Shouichi stab him to use the blood to fake Kurisu's death.
The research documents were later saved from a plane fire by Mayuri's metal Upa, which triggered the metal detector. Knowing this, Okabe obtains the Metal Upa before Mayuri, so that the Upa put into the envelope by Kurisu is a plastic one. The metal detector does not go off and the papers get destroyed by the fire, foiling Shouichi's plan.
He then swore vengeance on the Russian airlines, whom he blamed for the destruction of the research papers and was detained by Russian authorities. He is being investigation for stabbing Okabe.
Though it was not mentioned, it is likely that Shouichi worked with SERN in their time-travelling research in the Alpha attractor field.
In the Beta continuity shown in Steins;Gate Zero, where Kurisu's paper did arrive to Russia, it is revealed that he's more or less kept prisoner in the country to help with research and development of a time machine, and that the published version of the paper is actually an inferior copy written by Nakabachi himself to poorly mimic the theory and ridicule it among scientists. This aims to distract the rest of the world from the actual research, but also from the chaos ensuing from various organizations tracking down what remains of Kurisu - the paper's actual author, whose existence became apparent when Nakabachi's lack of actual knowledge shone through - in order to properly reconstruct the time machine.