@stretch22 The translator's note on that page explained it, it's the Buddhist swastika (which is a holy symbol, the arms are reversed from the Nazi one) and is a holy symbol normally, but has become slang with a variety of terms as well. (See here: https://kotaku.com/the-buddhist-swastika-becomes-popular-slang-in-japan-1822404738 ) In this particular case Goblin's making a visual pun, turning suman (a casual way of saying sorry) into sumanji, and contorting herself to form the manji character at the same time.
You'll see the manji character in manga and anime, as well as in modern Japan (it's used on maps to indicate Buddhist temples). It's perfectly normal there.