Indicates the forefront or the very first position; used to mean doing something before anyone else (e.g., 'first of all', 'right at the front').
避難するときは子供とお年寄りを真っ先に助けてください。
When evacuating, please help children and the elderly first.
彼は問題を見つけて真っ先に報告した。
He found the problem and reported it first.
真っ先に申し出るのは勇気がいることだ。
Being the first to volunteer takes courage.