In the West, gay men rarely appear outside of works aimed at... well, gay men. One of the odder cultural quirks of Japan (though it is slowly bleeding over to the rest of the world) is the use of young, homosexual male relationships as Fan Service for the girls. Works that focus on these relationships form a genre currently known by the English term Boys' Love, also called Yaoi. A Yaoi guy doesn't need to be a Bishonen, but there is a certain degree of overlap between the two character types. If there is a Yaoi Fangirl among the cast, she will try and invoke this trope.