The readings come from the 気 kanji (which you know) and the word 付く which you should know by now. Combine these together and you have the ability to read this word. Take note that the 付く part is rendaku'd, though, so it is a tiny bit different.
Don't pretend like you didn't notice.
I think I realized my feelings for Koichiko three days after we met.
I can’t believe you gave me your ice cream. I didn’t realize that you were so kind until now.