Naku
The letter ”鳴" means Cry, Sing, Chirp, Croak, Mew, Low, Bleat, Squawk, and Go in English. This is used only for aniimals, so human being never "鳴”. Another letter "泣（Naku）" is used as "Cry" for human being.
Shisyu's sensitivity is likely that "鳴" is deeper in sadness than ”泣".
How do you sense such a feeling in the above calligraphy ?