The Japanese phrase 'nante koto wo' roughly means 'what a thing to do' or 'how could you', and it is commonly heard in anime and drama when a character is confronted with something shocking or unforgivable. The parenthesised note in the original title points to anger, which matches the heated delivery rather than a polite surprise. Short clips like this circulate online as anime reaction sounds because the emotion is instantly readable across languages, and creators reuse them to add a dramatic Japanese voice reaction to memes, edits and commentary without needing a longer scene.