........but not my first Yanagisawa.
I play Yani soprano and tenor, and cheap Thomann sopranino and cheap[ish] gear4music bass. I only mention this as it is the reason I bought the Yanagisawa mouthpiece - I trust their stuff.
The mouthpiece that came with my sopranino was 'ok' but I thought that if I was going to upgrade I should do it whilst I was getting to grips with the instrument and while I could play all of the instrument with the supplied mouthpiece, the Yani does make it easier to reliably hit the very top notes [though, of course I would recommend playing a soprano top end reliably before getting a sopranino!].
It has a very clean sound, better than the supplied mp and has not added any coarse overtones which I was wary of with a metal mouthpiece - in fact I may next go to metal with the soprano [hey Thomann want to give me a discount? ;-) ] I am content with the purchase.