出典:Wiktionary
Ancient Greek δευτεραγωνιστής (deuteragōnistḗs, literally “second actor”), originally in Greek drama, from ἀγωνιστής (agōnistḗs, “a combatant, pleader, actor”).
Surface analysis deuter- (“second”) + agonist (“combatant, participant”).
deuteragonist (複数形 deuteragonists)
Much less commonly used in everyday speech than protagonist – while protagonist is a common term, deuteragonist is technical.