Upvote:1
Yes that is fine. According to this infographic from their website, you can even bring straight razors and knives in checked luggage, so a disposable razor will be okay.
Upvote:2
Yes indeed. I fly several times a year to Japan, generally landing in Haneda, and have had disposable razors every time in my luggage.
Customs officers - who inspect everybody and every piece of luggage, don't care about razors.