Same as Fig. 3 but for BH-549 and its host galaxy. This system is displaying an interesting feature since from high redshift to z ∼ 0.7, there is no stable disk and coherent gas accretion onto the BH. However, the host galaxy merges with another galaxy at this specific epoch as illustrated in the panel ②. After the merger, a gas of disk if forming but rotating in counter-rotation with respect to the stellar component. As a result, the BH spin aligns with the accreted material angular momentum vector and becomes anti-aligned with the galaxy spin as illustrated in ③.