How old is Shido in Persona?

Can you please clarify which version of the Persona franchise you're referring to, as there are multiple games and stories within the series? However, generally speaking, if we're discussing a protagonist named Shido from any of the Persona games, it's important to note that his age can vary depending on the specific title and story arc. For instance, in Persona 5, the protagonist's name is not Shido, but in Persona 4, where there are characters with similar names, their ages are often around high school or college age. Could you perhaps provide more context or specify which Persona game you're referring to, so I can give a more accurate description of the character's age?