Delicado translates to "delicate" or "sensitive". While it might seem like a common word, its specific use in the phrase "assunto delicado" (delicate matter/subject) is particularly poignant in this song.
Marília Mendonça uses it to describe a relationship that was perhaps doomed from the start, a "delicate matter" that shouldn't have even begun. This word encapsulates the fragility and complexity of the situation, making it a key emotional anchor for the song's narrative.
This is a sertanejo duet built on a breakup already half-finished by the time the song starts. The singer admits she never showed up for the relationship: "Sei que eu não fiz nada por nós dois" (I know I didn't do anything for us), "Fui deixando pra depois" (I kept putting it off). There's no villain here, just someone who ran out the clock on a person who waited.
The chorus turns that regret into a warning label: "Nosso caso é um assunto muito delicado" (Our situation is a very delicate matter), "Não deveria nem ter começado" (It shouldn't have even started). It's less a plea to fix things than an admission that it's over — the kind of song you play loud with friends after a breakup, not the kind you send to the person it's about.