Hello anon, sorry for a late reply–
To be honest, I am not sure myself– it might be from the drama CD where Clear sneaked in to his room and ate the peaches; they might think that their interactions would be really cute based from there.
It could be also their preferences to ship characters that their interactions aren’t really shown? I don’t really know how to phrase that though haha.
They might see Clear found Mizuki’s job as a tattoo artist interesting or they want to try a new ‘twist’?
Though it all comes back to personal preferences again ;u; Maybe (most of) Japanese fans prefer other pairings than MizuClear? I can’t really say…
Thank you for sending me an ask and I hope my answer doesn’t offend you (I’m sorry if it does, I don’t mean it orz).
Have a nice day!