Working on a translation, I wondered about the difference between kirei and utsukushii.
The Easy Japanese page on kirei and utsukushi notes that:
- kirei has a connotation of clean or neat
- utsukushii has a connotation of artistic beauty
And now I'm wondering if there's an aspect of intention?
Taka's Japanese Room says that utsukushii is more likely to be used for something like friendship (a beautiful friendship), and may have a connotation of elegant or charming (compared to neat, tidy, and clean for kirei).
“Kirei” can be used like an interjection to say “beautiful!” while “utsukushii” is rarely used for this purpose.