〜ずにはすまない (social obligation — cannot avoid doing)
〜ずにはすまない Formality Level: Semi-formal — formal writing, formal speech, analytical commentary Classical Origin: ずに is the classical negative gerundive (see Lesson 1: 〜ず). すまない derives from 済む ( sumu , to be settled/complete) in its negative form: "it does not settle/complete." The full pattern means: "without doing X, the situation cannot be settled/completed" → social or moral compulsion requires X. Structure Form Example V-neg stem + ずにはすまない 謝らずにはすまない Suru →...