I mean it’s ok not to shop a canon ship. I can’t say that the manga really addressed the buildup of their relationship very much (if at all), but Classic had an episode that told a bit of their backstory....However, it basically boiled down to the fact that they both felt like there was something missing, and Michiru had awoken herself then lifted the veil for Haruka. It doesn’t really talk about them as a couple.
Personally, I think they work very well together. Michiru is a calm and collected virtuoso and Haruka is a hot headed speed demon, but I think they balance each other. In Classic, I really love their repertoire, and I think they’re represented as a very happy couple. Again though, ships are all personal preferences. I’d be interested to hear who you think would be good with Haruka. 💖