It is not that realistic. Takamura drops from Heavy To Junior Middleweight doesn't he? I recall him saying he'd conquer 5 weight classes or something right? For pros, thats a drop from 201 lbs to 154lbs. 46 lbs. Light Heavy to Middle is only 2 weight class drop, which really isn't very drastic by boxing standards. (it's a little more than usual though). i don't know where you pulled those categories from.
Again, I don't know how you came to 83% water content. I don't know what your body is made of, but most humans have around 60-70%, with athletes at the higher end. (body fat has more water). Also... you're even less realistic than a manga. Losing 83% (fine, 70%) of your body weight by dehydrating lol. Yeah... if DYING isn't a major concern! Losing even 2% of body water can cause giddiness. Figures show 15% or greater dehydration is usually fatal.
Oscar Larios might have fought in 5 different weight classes. Heck, I myself dropped from 200lbs to fight at 140lbs. (Amatuer boxing different weight classes). The difference is IT'S OVER A LONG PERIOD OF TIME. Furthermore, and this is the cruical bit, once we're near a certain weight class, WE STAY THERE. You'd have to be an imbecile to drop to 5 weight classes for a match,
then PUT IT BACK ON while waiting for your next match to be decided, then have to lose it AGAIN and keep doing this for EVERY SINGLE MATCH.
I'm not surprised Takamura's skin is all dry like that considering just how badly he's dehydrated himself to make weight, actually. What's unrealistic is his rehydrating and getting it back to normal. And being able to fight. The man should be hospitalised or something.
You claim *I* don't know much about it? You, my friend, are the one who has his facts wrong. Don't point fingers at others if you don't know much yourself...