The thief stealing company technology was actually Kazuomi Isshiki. He was selling the components to Hiraguchi, an R&D employee at Myojo Technics, for a profit. The mouse robot created by Takeshi Tanizaki was actually designed as a security device to help him catch the person stealing company secrets. It was tuned to detect traces of a special ink (of a type which Isshiki kept at home, and which got stuck on his shoes) the culprit left at the scene of his thefts. Tanizaki met in secret with Makita, an HR employee at Myojo Technics, in order to find out the dates of their newest presentations, thus learning when the thief would strike next.
Upon catching Isshiki in the act, Tanizaki attacked the thief but was wounded in the process. As Isshiki attempted to escape, his rope came undone when the gas pipe he had tied it on was broken, and he began to fall. Tanizaki grabbed the rope in an attempt to save the culprit's life, but lost his grip on it and was hanged when the rope loop caught his neck, which Isshiki failed to notice. Isshiki break down in tears once he realize that his actions lead Tanizaki's death.