Did Japanese Buddhists once use sky burial? In the Chinese Wikipedia article on sky burial, there's a section saying that sky burial is illegal in Japan:


  棄屍嫌疑
  
  在某些地方，天葬的行為，可能觸犯遺棄屍體的罪行。
  
  日本
  
  刑法第190條（死体損壊罪）


Google translation:


  Dumped suspect [My assumption for translation: Illegality of
  abandoning bodies]
  
  In some places, burial behavior may violate abandoned corpses offense.
  
  Japan
  
  Penal Code section 190 (dead body damage Huai crime)


Did Japanese Buddhists once use sky burial for their dead? Or is the ban just a broader ban that just happens to include sky burial?
I was curious about this question and I found some sources that might answer this question more or less:

...in ancient Japanese society, prior to the introduction of Buddhism and the funerary practice of cremation, the corpse was exposed in a manner very similar to the Tibetan sky burial.

This excerpt is from the wiki article on Excarnation.

The following link opens to a part in an ebook that might help answer this question:

https://books.google.com/books?id=CZM2AQAAQBAJ&amp;pg=PA118&amp;lpg=PA118&amp;dq=Excarnation+~Japanese&amp;source=bl&amp;ots=DF_qKCS7PC&amp;sig=H9zvNsP284SQteLueDyDmyvWmjI&amp;hl=en&amp;sa=X&amp;ved=0ahUKEwjQurPevcDKAhVW2mMKHS6ADKkQ6AEIMTAG#v=onepage&amp;q=Excarnation%20~Japanese&amp;f=false