A known leaker named Zippo has leaked a new game character with Goro Akechi from character 5. As you might expect, the game in question is not character 6, which has yet to be revealed or even confirmed, but when it does, he’ll almost certainly be playing a new character. In other words, it would be a spin-off of character.
Zippo is known to the community character. He disclosed the existence of the remaster of Persona 4 Arena Ultimate, for example, among others. According to him, this new game will not be an RPG and will feature Akechi, focusing “on his adventures and star detective skills”. Unfortunately, that’s all Zippo said. It’s unclear when the game will be revealed, but if you read between the lines, it looks like its reveal isn’t too far off. As for the supposed protagonist, Goro Akechi is shown investigating the Phantom Thieves in the original plot.