I've tried for a while minato hokage in arena and i have problems in understanding how it actually works.

For how many rounds does it actually last and when, during the round, it disappears?

Because seems, by default, that lasts 2 rounds, but there are times (also after round 1) where tag simply disappears at the beginning of the following round is applied even if there's no healer or cleaner in the enemy team.

Why this happens?