On October 13, 2019, Yeonsang announced via his personal Instagram account that he would be starting his mandatory military service on October 17, 2019.
Since he is serving his military service, MBK is debuting a new boy group, and MBK hasn't released any updates on him via the MBK BOYS Twitter, it is assumed he left MBK in general. Although, it's not know if he's left the entertainment industry completely.