"Tgirl Japan" is a combination of two terms: "tgir" and "Japan." In the context of pornography, "TGIR" stands for "Transgender Girl," referring to an individual who was assigned male at birth but identifies and expresses herself as a female. This term can be used by people who are transgender, genderqueer, or non-binary, among others.
Adding the word "Japan" to this tag indicates that the content is specifically related to Japanese transgender girls. It may refer to performers, scenes, or films featuring Japanese TGIRs in explicit sexual situations, or it might simply be a reference to the country of origin for the particular content being described.