For us, its Sakura of Tokyo, in Naperville, IL
This is where my wife and I had our first meal when we were dating. She never had sushi or Japanese food before and love it. It became our regular spot, usually going once or twice a month. One particular day, about 4-5 years ago, we notice something was odd, the older couple that tended to the cash register and seated you were no longer there, the waitresses were all different, along with the sushi maker. Service was extremely slow, it took almost 2 hours for the meal to be completed. The food was good, no problem there, but it was no longer the same. We've never found out what happened to the previous owners or staff, but we certainly missed it. The restaurant is still there, and it appears that it has gone through 2 ownership changes. The couple of times we've tried it the menu was changed and it was no longer the same for us.
Luckily, we found another one nearby, Raku Sushi, that is just as good.
If anyone is familiar with what happened to the "original" Sakura of Tokyo, or know if they re-opened in another location, please PM me.