losing one's reason due to love; love-induced blindness
Describes a state where romantic passion clouds judgment, leading to irrational behavior or poor decisions.
恋の闇に落ちて、彼は仕事も手につかなくなった。
Falling into the darkness of love, he became unable to focus on his work.
恋の闇とはよく言ったもので、彼女は周りが見えなくなっていた。
As the saying goes, love is blind; she had lost sight of everything around her.
A compound of 恋 (love) and 闇 (darkness), literally 'the darkness of love.' The expression figuratively refers to the mental blindness or loss of reason caused by intense romantic feelings.