An outgoing, imposing but very kind man, Dr. Leskinen is both a respected scientist and a "big child", according to his assistant Maho.
Although Leskinen appears to be friendly and childlike, which is indeed part of his personality, he secretly works for the intelligence group named Strategic Focus, which is seeking information on time travel due to Dr. Nakabachi's recent theory that keeps him working in Russia, in order to sell it to all of the world's countries. This job reveals an uncaring and extremely dangerous side of his, and shows him to be outrageously unscrupulous. Leskinen used Maho and Katsumi as subjects for human brain experiments, and is ready to torture Okabe to extract information on time travel from him.
Leskinen is the mentor of Maho and Kurisu at the Victor Chondria University in the United States. In Steins;Gate 0 in the β (Beta) timeline, he brought Maho to Japan to assist him in his lectures about the Amadeus system. He speaks English in his lectures while Maho translates his words to Japanese, although he is shown to be able to converse in Japanese using a translator device.