I actually have a question about this. I know this is pure semantics and all, but I am curious to figure out the mechanics of this vocabulary!
Me, I love all of the ***48 girls--and I've been a fan for years, but I've always been pretty wishy-washy with saying who I like best (I've done "rankings" before and stuff, but it has never been precise, I've never taken it seriously, and I quickly end up disagreeing with myself...because I just liked them all so much I couldn't pick.) I can say to myself: "Yeah, when it comes down to it, I probably like Yuko better than Acchan" (obvious example haha), but that doesn't really mean all that much, I love them both.
So what I am saying is that it has been this way for years, but recently I've encountered something a little different. I had basically stopped using the internet for awhile, real life etc was getting rough & all, and accordingly managed to miss SDN48's actual debut. I didn't end up getting back up to speed on the ***48 wagons for a few months, but once I did I found myself completely fascinated by Serina. It's weird, because I guess I would say that I "like" (to use the same example from before) Yuko more than Serina, like I can say to myself "Yuko is probably more the kind of person I can easily imagine being friends with." But I think about Serina way, way more often. I find myself watching her videos, looking up her pictures, more than almost any other idol. And, again, it's weird, because I can't pinpoint what it is that keeps drawing me--I can't list off any "traits" that I like about her the way I can for almost any other idol, I can't imagine hanging out with her--I can't imagine or articulate much of anything! I can't just say "oh, obviously I like this, this, and this." I'm not sure what I "like" about her at all. I just find myself, again and again, spending time thinking about or looking at her, wanting to spend (and spending) the little money I can on her merchandise as opposed to any other idol...I bought her photobook after I'd vowed to not buy a photobook again until I graduated school, for example, just on a whim--the only photobook I've purchased since 2009. Furthermore if I were to write a fan letter to any idol it would have to be her, mostly because I'm curious about her in a special way. But it's not just curiousity, that wouldn't be enough to hold me this long and this intensely. I am also obscurely enamored. I'm not satisfied with basic profile information. I want to share my words with her and hope to someday be able to read hers--to share with her, to watch over her, somehow. So....
Is THAT an oshimen? As opposed to just a "favorite member" or "an idol I like"? I'm just not sure if that's how the term "oshimen" would be used, exactly, although I do definitely feel like there's something different about how I feel towards her, less like she's my "favorite" and more like I'm in love or something lol
That would probably be it yes
It doesn't have to be some "fall in love" thing or something like that of course, but it's the one girl who ranks above all others - even a handful of girls you can call your "favorites". So you could say it's like this in terms of hierarchy: 1) Oshimen, 2) Favorites, 3) The rest.
I want to share my words with her and hope to someday be able to read hers--to share with her, to watch over her, somehow.
With these words specifically. I would say, yes -- you found your oshimen.
Like Krusha said, it doesn't even have to have anything to do with falling in love specifically.
Someone who for some reasons or another keeps standing apart in your mind from any other girl. There will always be members you really REALLY like (hence why I just had to make the "she's not my oshimen but..." thread : P), but if there's one that just....shines above all the others to you. Then that's your oshi. Someone who you find thinking about all the time...someone's who just fascinates you. Often times it's the person who just seems to transcend the "I like her cause she's pretty" line even if you can't pin-point exactly why yet.
It took me about a month of constant thinking to figure out exactly why my oshimen was my oshimen. It was picking away at my brain everyday and I realized I just had to write it down on paper whenever something would come to mind -- everyday I learned something new.
I was finally able to put all my thoughts together in some palpable sense and I've been in the process of typing it all up these past 3 days. And it's been really emotionally fun to write up! I know it sounds weird, eh?
I hope you have fun fully supporting your oshi.