I have a protagonist who is biracial (mixed-race Caucasian-east Asian ancestry) living in the United States. I have a good idea of what their face and appearance looks like; they’re the kind of person I’ve heard real-life mixed-race people of white-Asian descent describe as “Schrodinger’s Asian”: white people think they look white and Asian people think they look Asian, and depending on how the character does things like style their hair they can either look really white or really Asian, even to the same person.
My concern is how do I convey to the audience that the character is biracial? This is a particular issue because the character has an easy time “passing” as white, and thus it’s not likely that the other characters would notice. Contrast this with other potential mixed-race combinations, where it is easier to signal they are biracial by putting in a brief mention of skin color, which is something that is easy to mention in a description of a character. It’s honestly really, really hard to convey that someone is Asian or mixed-race with Asian ancestry without sounding like a 20th century phrenologist, and most human beings don’t speak that way when describing people’s looks. I find it hard to even describe someone who is full Asian without it sounding very strange and non-conversational. The closest I could think of is when there is a character that is supposed to be a very light-skinned Latino/Latina, and the writers pepper in Spanish into their dialogue to show that they are Latino/Latina.
Additionally, the character is an amnesiac runaway, so I cannot easily do things like show their non-white relatives, have them describe experiences relating to a specific east Asian culture, have them offhandedly use phrases in another language, or even use their first or last name to show that they are biracial. E.g., Anne Boonchuy from Amphibia is Thai-American, and this is conveyed to the audience both through her last name and from her mentioning trips her parents took her on to visit family in Thailand. If this were a visual adaptation my character's biracial ancestry would be pretty clear, but this work is in a written format.
The main reason this is of concern to me is that if my story ever gets popular enough to get visual depictions or even some kind of adaptation (yes, a pipe dream I know), given how people have been reacting to other fiction recently there may be a huge amount of backlash from people claiming that I “racewashed” the character as a diversity stunt. E.g., the whole “black Hermione” thing that popped up about a year ago, or what’s going on with Death in Neil Gaiman’s Sandman adaptation (both of which given the context and statements by the authors statements do kind of come off as shallow publicity stunts). When the truth is that no, I don’t care about “muh culture war” in either direction, I have a specific idea of how this character looks and this is the way that they’ve always appeared in my head. I’m more concerned with avoiding such a controversy in the first place, because I’ve noticed such a thing results in the controversy overshadowing the actual quality of the story, which is the part I actually want people to notice.
I know that there is this question on Writing SE, but I am not sure if I am asking the same thing as they are given the comments suggest that the question has been edited a large number of times. There are also some unique difficulties in specifically conveying a character is of mixed Asian-European ancestry in Western countries, given most people in these countries often don't see these individuals as anything other than white.
Given this, how can I convey the character is biracial with mixed Caucasian-Asian ancestry in the text, particularly when it comes to establishing the character’s appearance in people’s minds?