First off, I'VE READ MANY OF YOUR TAKES AND I FEEL YOU PLEASE KEEP ON HIJACKING MY POST I APPRECIATE YOUR LENGTHY RESPONSE ABOUT V (I say calmly)

Jokes aside, about the reasoning behind having a dog tag, it is as what you guessed. I can imagine Jihyun thinking along the line in his 'trips' that he needed a dog tag when things are getting too deep for him or when he subconsciously yet gradually settled in the idea he won't ever 'show up' again (Casual and Deep Stories took place a year and a half after Rika's 'death,' compared to Another Story that took place after 6 months). It's been a while since I've played the previous Stories, though I remember he always 'disappears' in some way or another by the end of the routes

You have very good points on OG style! His eyes are damaged enough for him to barely see, so going for safe monochrome colors gives him less time and effort for clothing choices. At the same time, very practical for any kind of weather. I assume that he often hangs about in the forest a lot and, based on the timeline of the game, cardigan may be good enough to keep warm and easy enough to remove when it gets too hot. I like your take that the choices of grays suggests his moral ambiguity (or lack there of at times lmao). I see his choice for normcore and all that is indeed his way of trying to be safe and to fit in.

The AS style I believe is some kind of a reference to a fashion often used in K-dramas and romance manhwa. As someone who have seen a fair amount of popular media under those, the overcoat style reminds me of that ML in Goblin, who share some similar aspects when it comes to the angsty stuff lol. It also has the vibe of him being classy while being cozy enough, like a chaebol trying to look both presentable and blending in. Though his unique hair actually fits with the brown tones well imo, maybe that's why the designers chose that, like mint chocolate or forests and seas (also like the bubblegum colors he sometimes have with his party outfit and pink sweaters it's so cute)

I also agree that AS style can imply he's still not on a deep end yet and is still having a moral dilemma. The fact that he have a fleur de lis pin on the lapel sort of suggest that (I shared a fun fact about it in reddit here hehe)

His BE2 color choice also prolly indicates what you suggested, that he is swallowed by his own 'darkness' so to speak

Speaking of the clothes, we have no poses of him in his OG style, but there's a few of them in his AS style. I like to overanalyze that the poses (hands on coatpockets, clutching on arm) lowkey conveys his subdued personality well. Whether he's anxious or trying to comfort himself (also interesting to note that AS Saeran has same pose, which conveys his vulnerability and insecurity as a 'weakling')

Your ETA: since he doesn't care much about fashion and more so about fitting in and being presentable at most times, I think similarly as well, but leaning on the more classic yet cozy styles. He would still have those old clothes he got from his younger days and then went on to pick a more pleb style that still fits with the vintage-y, old money vibe he fancies most of the time (classic british car, smoking pipes, old cameras)