I don’t think this is a plot hole yet, but I don’t really know what else to call this.
Sometimes I wonder how Furuya is even Japanese because he doesn't look the part like ONE BIT. The only Japanese thing about him is his girlfriend, which is literally Japan itself (please don’t think of the alternative).
Let’s look at other half-Japanese characters. There’s Elena, who’s probably half or fully foreign. Honestly, Furuya looks more like her kid than her own kids do. Sure, their dad is Japanese, but look at Akemi - she looks like any other normal character we’ve seen. Shiho looks a little different because of her hair and probably her eye shape, but it’s not just exclusive to them. Look at the Akai family. Mary, who is Elena's sister, looks like her twin and she married a Japanese guy from what I remember. Yet not a single one of her kids turned out with blonde hair like hers. So it makes me think Furuya is probably the spitting image of his foreign parent, but even so, did he really not inherit anything from his other side besides the nationalism?
Also, the total lack of connection to his other culture is wild. Look at mixed American kids, for example. They grow up in America and everything, but they still pay tribute to both their heritages at the end of the day, even if they don’t know crap about one side (obviously not all) They might at least try, especially as adults. But Furuya? No, he’s fully locked into one side, like he refuses to acknowledge anything else. Putting the bullying aside - I’m probably going to make another post about that later, but I briefly mentioned it here.
I’m not even sure what the main takeaway of this post is tbh. I know genetics are complicated/vary. But also, is it possible he just got his tanned skin from his Japanese side like Heiji? At some point I honestly thought Fusae might be Furuya’s long-lost mom.