From what I can gather, the identity of Takeda's Persona actually hasn't been revealed in ANY official capacity, including side materials in Japan. The closest I can find to hints are the following two names: first is that on a site called mystery meep (specificially here) as well as the tvtropes page for this very comic, it is listed as Noppera-bo, though for what reason is not provided. Second, and what I find more compelling, is an unused Persona found in the game's data called Shikijirou, but there's no images for it in the files from what I can tell, so this is mostly just conjecture. There's also unused data for a demon version of Nyarlathotep, and given how Kandori's version is clearly different from the version that the heroes can summon, maybe it's the same one but got repurposed as Kandori's Persona. And by extention, perhaps a similar deal happened with Takeda's Persona, where the players were supposed to be able to fuse or summon an equivalent of his Persona following his defeat but it never occurred in the final product. However, this is just a theory, and in all likelihood nothing more than me just trying to make some connections where there may be none. But until I come across someone coming up with a more-compelling argument for something else, this second name is basically my headcanon now.