>>1491220It was ugly, with a lot of dead ends and faffing about. When the obvious searches didn't work, I resorted to skimming through danbooru with "solo blonde_hair ahoge sword -fate_(series)". Fortunately, that sword stood out, and I was able to find it pretty quickly and nail down the character. Then it was a matter of finding that specific image, which took a surprising amount of time, because the only tagged database I could find it in was zerochan, and that was also the last place I looked.
Someone who's into YGO probably could have found it in minutes; it ended up taking me a bit over an hour.