About that "wo" hiragana.....
Those who've learnt a little about hiragana know that they come in regular series of 5:
"a" "i" "u" "e" "o"
"ka" "ki" "ku" "ke" "ko" etc....
before 1946, there existed a series like that, although incomplete:
"wa" "wi" "we" "wo" (not that there is no "wu" -don't ask me why, LOL)
in 1946, in an effort to simplify writing, the Japanese Ministry of Education made "wi" and "we" obsolete. "wa" remained what we know today, while "wo" became "o" and, as was already pointed out above, remained only in use as the particle that singles out the object marker (pronounciation as "wo" from what I understood, can still be used for rhythm purpose, i.e. in songs or poetry -but I'd need to check on that one)