A bit late but here goes.
OK, I don't want this to sound mean, but you're being a bit pedantic here. Of course it will lead to it. It's just not very effective. That's why I said "at best it will expand your vocab". I read J-news, and read manga/play games in Japanese. You're pretty fluent (from what I understand anyway), so you and I both know very well that it does not translate well at all. In fact, I'd go as far to say that they're both completely different styles of reading and the only thing that translates is they both have particles in them. Reading something like My Hero Academia is totally different to reading anything of importance on yahoo.jp. Except the comments.
Like I said. If it's your goal, go for it. Just don't kid yourself; cause you'll be in for a rude awakening later.
OK, this is another great point and anybody who is studying Japanese seriously, or plans to, should take note. The bolded here, Alanae kinda touched on, but Spork articulated better (sorry Alanae, don't be mad). HOWEVER - Alanae and Spork will back me here - the benefit from this comes only after you've got a moderate degree of grammar knowledge under your belt. I assure you (again, speaking from experience here), it will just fall straight out of your head otherwise. Because it's garbage. Do yourself a massive favour. Stick to the books for just a little bit more. Tough it out. Finish the Genki 1 and 2 or something, I don't know. Then buy an N4 study book, absorb the grammar. Then try reading One Piece. Otherwise you'll waste your time, time you could use more effectively.
Having said all of that, you can do whatever you want, I'm just giving advice, from experience.
Most of my reading ability comes from reading all sorts entertainment, be it manga, visual novels, light novels, etc, and all the articles/dictionary entries I read explaining the grammar, phrases and words I didn't know yet.
I think that more so than the specifics of what it is you're reading exactly what is far more important is just to have the dedication to look up, ask about, try to understand the things (words, grammar, etc) you come across that you don't know yet and to make sure to look them up again whenever you didn't fully remember them the last time.
Reading the things you want to/care for is a great help in sustaining that determination
If you can do that, then wont matter which/how many study books your stare at before trying to read things.
(That said, having read up on some basic grammar will make it a lot easier to actually manage to do so and will save you a lot of time in struggling hard with things that you'd probably would have had properly explained to you by a beginner guide/textbook in the span of a few pages) .which is why I keep recommending people to spend a week or two to read through tae kim before taking the plunge).
You can think of this as being a dynamic form of textbook, as it'll make you study things in the order of them being important to your current situation and with the more commonly used grammar being more likely to pop up (and thus you'll learn them faster).
Being able to immediately apply the knowledge you get right away in "real" situations also does wonders for how well
The point I've been trying to make is that learning from reading things works additionally, as you read different things from different writers you keep adding new things to your knowledge base while getting better at the act of reading itself also.
Once you can read decently, which is something you can achieve from reading enough of whatever (it's not like the Japanese language switches to using different sets of grammar/rules/etc based on just what medium its currently residing in), filling any holes in your vocab becomes as simple as just switching to focusing on reading works in the field that contains them for a bit.
As much as I'd like it to be true, we're not all like I'm an expert, if only because we don't have as much time and energy to devote to the whiteboard method as he used to have. Plus that method doesn't actually teach you how to read.
Probably won't be much of a surprise for me to say this, but I have to say I really dislike the whiteboard method. It's almost impressive in how far it goes in draining out every bit of fun there is to be had in what could be an enjoyable experience of learning a new language, replacing it with a hellish grind that is likely going to burn out many people and help further spread the idea that Japanese is impossible to learn.
All the respect to you if you can pull it off doing this, but from my point of view it seems like such a waste of what could have been a fun time.
Besides, when I think back on how I learned English as a second language, I owe 90% of my proficiency to games, random media and internet forums. Not reading the news or painstakingly long rote memorization sessions. The only difference here - and admittedly, it's a pretty big one - is that Japanese is very different from our languages and puts a ton of emphasis on written language. So don't fool yourselves into thinking you can completely do without some amount of dry memorization/practice exercises. You'll definitely have to do a bit of that too, and to stay motivated... But have fun as well, especially if you're not planning to use Japanese for professional reasons.
While there are things where straight grinding it out is going to be unavoidable (kana for instance), I think that for most things you can kind of avoid it by combining it with more interesting things, grammar you can learn by combining it with the reading of interesting (well, they were interesting for me at least) articles and applying it, recognizing kanji and learning vocab you can learn by combining it with reading things, learning how to recognize words through listening you can combine with listening to things with voice acting or with Japanese subs, production can be combined with communicating with people, and so on.
The big omission here is the handwriting of kanji, but even with that you could pull it off to some degree by trying to writing out thing that are some what relevant (eg. shopping lists, diary entries, letters, etc) instead of only grinding out walls of kanji.
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re: furigana
furigana only becomes something that will screws you over if you let it be.
two scenarios:
1) you use the furigana as a method to quickly obtain the reading of the word without having to spending ages radical/handwriting search it (which quickly becomes unbearable if you have to do it often enough), when doing this you make sure to look at the kanji that belongs to the word underneath and try to link the reading to it.
result: good, sooner or later you'll start ignoring most furigana because its just getting in the way or get annoyed at it because there's so much of it covering the screen everywhere (for a good example of the latter, see the japanese jlpt site, I mean just look at
it)
2) You fully ignore the kanji and only look at the easy to read furigana on the top as if it were a bridge over a river of strokes.
result: bad, you end up knowing a lot of vocab which you wont be able to recognize when its written in kanji without furigana to help you.
Just like with the avoiding npc dialog and other sources of text in DQ, it's something that comes down to whether you can avoid the temptation to take the easy way out.
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