The meeting between L'Arc-en-Ciel's Haido and Tomorrow X Together

Haido, the vocalist of Japan's representative rock band L'Arc en Ciel, met Tomorrow x Together. Looking at the photo, they are making a V pose together affectionately. It's warm and nice to see. Haido also looks so young, as if he has been shunned by time. I was wondering how they met, but I heard that Haido personally worked on SSS, one of the original new Japanese songs. They met because of a musical collaboration.