I had some left over yuzu, so I removed (a lot) of seeds, sliced it thinly, and mixed it with an equal amount of honey and sugar by weight (mixed with 50% honey, put it in a steralized jar, and then topped with 50% sugar). This'll turn syrupy and slightly ferment. It's usually mixed with hot water as a tea, but it can be used for other things.
Edit: After reading what I wrote it seems like it could be confusing. For 200g of yuzu you'd use 100g of honey and 100g of sugar.
This sounds great! Unfortunately, I've never seen a yuzu at the grocery store and there are no Asian markets near me. I'll definitely be looking for them though!
You can make it with other citrus or really any other fruit. Just follow the 1:1 sugar:fruit by weight ratio and you're good. I've seen people make it out of all kinds of things.