Is it porn? If it isn't he is just a normiefag and you decide what to do next.
If it is, tell him japan, the country that allows porn of anime highschoolers and loli the most, is on the record of child rape right now(
https://news.yahoo.co.jp/articles/f4bbd6baeb1d2c90613655a2d798903e93e0d2f9), even while being a country that has a culture that doesn't look up on reporting sexual assault cases.
Tell him if he wants to stop consuming porn as often, if he even listens to you, to maybe consume shit that lowers his libido like spearmint tea