inscrutable
$ \mathrm{inscrutable} /ɪnˈskruːtəbl/
adjective
​(especially of a person's expression) impossible to understand or interpret
He was wearing that inscrutable look again.
Her face had become inscrutable.
inscrutable to somebody
Unfortunately, this language is largely inscrutable to non-specialists.
Word Origin
late Middle English: from ecclesiastical Latin inscrutabilis, from in- ‘not’ + scrutari ‘to search’ (originally ‘sort rubbish’, from scruta ‘rubbish’).
e.g.
/fe3hdialogue/散策・金鹿の願い The Golden Deer's Plea#63f4a699bdb0e50000bbb6e4
/fe3hdialogue/Jeritza×Constance#62e11c09bdb0e500009001d4