Marriage proposal at the concert on 21 (Takuya's Bday). We do not know more details of this proposal, but it must be something great for the couple. She said "Yes". :'DDD
Here the translation of fiance's tweet:
"My proposal was successful.
The 14/12/21 was a very important day. One day I will never forget. Many words of celebration... All Crew, the entire team of UVERworld, I'm filled with feelings of gratitude. Thank you very much".