Arcana
Persona 3 is heavily based on the thirteen Major Arcana of tarot cards. Each Persona user in the game represents a different arcana, which is representative of their personality. Due to the differing social links between the male and female protagonist, Shinjiro ended up having two different arcana depending on the route being played. If the player choses the male protagonist, Shinjiro is the Hierophant. If playing the female route, his arcana switches to the Moon.
The Hierophant

When I was doing research on this arcana, I will admit I wasn't immediately smacked in the face with a sense of "hey, this sure sounds like Shinji!" However, the more I read and thought about it, I think parallels can certainly be drawn to his character. Shinjiro does have the respect of SEES because of his experience, calm demeanor and power. He really is not a natural leader by any means. However, I would argue he has the role of offering assistance, advice, guidance and teaching to Akihiko in his own way. He does whatever he can to help Akihiko and tries his best to scold him at appropriate times in order to ensure he learns his lesson. He is certainly mature, formal and conservative as well. Shinjiro also can be considered a "not overly good, but definitely not bad" kind of character. He is a very good guy but his actions and words may not always come off that way at a first glance. He is also responsible for the death of an innocent woman. While he didn't kill her on purpose, he certainly questions whether he is still a good person afterwards. I think the theme of doing the right thing is something that strongly resonates with his character. He desperately wants to do the right thing by atoning for the past, even if it costs him his life. I laughed when I read the part about the need to conform to rules because of how foul-mouthed and independent Shinjiro likes to be. I'd say Akihiko would definitely agree with that piece of advice, though! I liked how some sources said the Hierophant was related to the point in time where a person forms their identity. After Shinjiro kills Ken's mother, he tries to forget everything about who he was and creates a new lifestyle and sense of self. While he was not entirely successful in creating a new identity, it was certainly a turning point in his life that changed him forever.
The Moon

The Moon is definitely representative of the side of Shinjiro seen through his social link. In fact, I think the Moon is a better reflection of his true character where the Hierophant is what someone would see at the surface level (which makes sense, I suppose, since his perspective and feelings were not shown until he became this arcana). Becoming closer to the protagonist throws him into a state of confusion, conflict and doubt about his resolve and the way things should be for him. Saying Shinjiro is going through a difficult emotional time and is haunted by the past is an understatement. He is practically drowning in negative emotions and completely chained to the past. The card being representative of a choice to break from reality or a chance to better oneself could represent the crossroad Shinjiro came to after the death of Ken's mother. Unfortunately, he chose oblivion and escape from reality until he resolves to atone for her death with his life. Lastly, Shinjiro even says himself he never would have imagined re-joining SEES a few months before, which can be connected to the Moon being associated with doings things one would not have considered in the past.
RESOURCES:
Tarot Card Interpretation & Meaning
The Hierophant @ Keen
The Hierophant @ Learn Tarot
The Hierophant @ Wikipedia
The Moon @ Keen
The Moon @ Wikipedia
b a c k . c l e a r . f o r w a r d Paint it Black is © Samantha, however Shinjiro and Persona 3 are © Atlus and other rightful owners. Paint it Black is a part of AFTER-DEATH.ORG.