"No, no, no. Even as a guess, that sounded way too ridiculous..."
Pinching the bridge of his nose, Conan hurriedly deleted the images Heiji Hattori's description had conjured in his mind and firmly rejected the idea.
He knew Tangze's cognitive abilities were extraordinary, but no matter how extraordinary they were, producing a doppelgänger was still far too out there...
"Then how else would you explain your theory? In the first place, suspecting that Tangze and Joker had an extremely deep connection, or might even be the same person, was ridiculous enough." Heiji waved a hand and bluntly said so.
If it was Joker, then yes, he was an excellent master of disguise. He had helped Conan solve the problem of appearing in public many times when Conan could not use Shinichi Kudo's identity. Playing different roles was not a problem for him, but that meant Joker would need to constantly maintain two identities and accomplish all sorts of things, especially in front of people like Conan, who knew something about his identity.
Never mind the difficulty involved. The workload alone was staggering, and Tangze would also have to portray another character completely different from his own personality. Was there really any need to push himself that hard?
Based on their understanding of the Phantom Thieves of Hearts' work, never appearing before the public at all would actually have been the safer choice...
"I admit there are many flaws in this suspicion. There are plenty of reasons that could prove the two of them are not the same person. But the more I sort through my past memories, the more details I find that can support my theory as well..."
Conan pressed a hand to his forehead, repeatedly recalling every interaction he had had with Joker. His voice carried hesitation, as