The break was very clean, at the ridge closest to the bottom of the cup. There's still a little nub left. So, it looks like it didn't tear, but rather that there was just some kind of defect (?) and it just popped right off when I pulled. I haven't had it for very long (less than a year), and I can't think of anything that I could have done to it that would weaken the material.
I'm a little disappointed because I use the stem to make removal easier. Since my period just started I'm going to give it a try without the stem. I was able to remove it just fine last night, so maybe there is really no need for the stem. Just a little annoyed that it broke off at all!
I just looked up Yuuki cups on ebay and in the listing it says cups can be returned up to 8 to 12 months after purchase...has anyone returned their Yuuki? Were you able to get your money back or exchange it?
Since they're not terribly expensive, I might keep it anyway and buy another one with the stem in tact, but I'm just curious in case the lack of stem is really a deal-breaker and I'm not able to use it at all.