I'll say it straight out - I'm a citrus whore, and love it in all its shapes and forms.
After reading
this article yesterday, I went in search of the elusive Dekopon citrus and found it at the first store I visited:

Tried a sample that was offered - the pith was practically non-existent, and the flesh was silky and very juicy. It really was incredibly sweet (maybe even
too sweet - I like some acidity). Bought two - will have to try them in a few days when they're ready.
The fruit may be available at Mitsuwa in Arlington Heights?