Can I still apply for UCs? Do I fulfil the foreign language requirements?

yes, for Berkeley, they want you to reach the third level of a language, and not necessarily 3 years of a language. For other UCs it specifies 2 years but the wording is a bit nebulous. You should be fine, I’m pretty sure with having taken a Level 3 of Japanese and nothing else.

Completion of high school foreign language (other than English) through the third year of instruction - Minimum Grade: C-

http://guide.berkeley.edu/undergraduate/colleges-schools/letters-science/foreign-language-requirement/