鉄石 てっせき心腸 しんちょうでしょう
tesseki shinchōdeshō

Noun
Desu Copula

Expresses probability in a polite manner ("probably…") of 鉄石心腸

1. Probably has a heart of stone.; Probably is resolute.; Probably is unyielding.

Polite
Presumptive
Conjecture