https://www.allkpop.com/article/2018/08/btobs-changsub-and-b1a4s-sandeul-cast-in-musical-iron-mask
BTOB's Changsub and B1A4's Sandeul cast in musical 'Iron Mask'
btobchangsubsandeulcastmusical
https://www.koreaboo.com/news/btob-changsub-ot7-gesture-statement/
BTOB's Changsub was recently seen showing the OT7 gesture during an online concert. He personally addresses the doubt cast on them due to this.
btobchangsubaddressespublicregarding