Confession
noun, verbal noun, の adjective
To announce something and make it white is to make a confession. Think of a completely blank sheet of paper - your confession clears all the announcements from the sheet of paper, making it white. This word is often used when someone confesses romantic feelings for someone else.
こくはく
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
僕には告白する勇気はありません。
I don't have the courage to confess.
今までに何回自分から告白したことある？
How many times have you confessed your feelings to someone first?
彼女はついに自分のしたことを告白しました。
She finally confessed what she had done.