Mandarin subbed - KAT-TUN Debut 15th Anniversary Special Interview
https://www.bilibili.com/video/BV1Qg41177qR
This's exclusively only available in the fanclub CD + DVD / Blu-ray version of Roar
I definitely will watch it & I will not be surprised if it's like the prelude of Nanisuru? KAT-TUN , content wise