Maiko

This pairing comes from Avatar: The Last Airbender and features Mai and Zuko, with real grounds of pairing as the two were childhood sweethearts. Throughout the series the two shared several kisses and there was a memorable scene where Zuko leaves a letter for Mai when he needs to leave for an important task; while Mai takes this as a "break-up" letter the two later get back together. This relationship was canon.

It was primarily used to show why Zutara would never happen.