Hello, when i first started looking at Japanese drama on the article, i just noticed that all of the J-Drama and movies are all G-Rated, espcailly its violence, kiss scene being g-rated too as well?

Mm no. 

Honestly Idk what kind of articles that gave you that silly idea. 

There probably lack of parental guides in dorama that circulated online but there way to look up which comparing with the time it aired. More late dorama is usually have more vulgar contents than prime time, mean no way show like shimokita glory days or even gilgamesh night is g rated

While for movies there plenty of that if just  for example 




This just brief look from movie battle royale (2000)

https://m.imdb.com/title/tt0266308/parentalguide/certificates

While late show like shinya shokudo got tv-14 in US

https://m.imdb.com/title/tt6150576/