“…Thus, z > 6 quasars, seen when the universe was less than a billion years old, are a unique beacon to study SMBH and galaxy formation. To date, more than 200 quasars with rest-frame ultraviolet (UV) magnitude M 1450 −22 mag are known at z > 5.7 (Inayoshi et al 2020), most of which were discovered by wide-field optical and near-infrared surveys (e.g., Bañados et al 2016;Fan et al 2001Fan et al , 2003Jiang et al 2016;Matsuoka et al 2016Matsuoka et al , 2018aMatsuoka et al , 2018bMatsuoka et al , 2019aWillott et al 2007Willott et al , 2010. The sample includes eight quasars at z > 7 (Mortlock et al 2011;Bañados et al 2018;Wang et al 2018Wang et al , 2021Yang et al 2019Yang et al , 2020Matsuoka et al 2019aMatsuoka et al , 2019b.…”