expression, ichidan verb
turn over a new leaf; reform oneself; change one's ways
Idiomatic expression meaning to fundamentally change one's attitude or behavior for the better, as if replacing one's soul. Often used when someone resolves to abandon bad habits or a negative mindset.
彼は心を入れ替えて、まじめに働き始めた。
He turned over a new leaf and started working seriously.
As if she had reformed herself, she stopped being late.