indifferent, heedless, careless, unconcerned

💡 Nuance & Usage: 本来なら気を配るべきことや、他人の評価、周囲の状況などに全く関心がないこと。多くは「無頓着な人」のように用いられます。(It describes a complete lack of concern for things one should normally care about, others' opinions, or surrounding circumstances. Often used in phrases like 「無頓着な人」 (an unconcerned person).)