Pair of detections aligned along the line of sight, as detected in the Y-band run. Members of the foreground cluster, located at z = 0.47, are indicated by cyan circles. The yellow squares indicate background cluster galaxies (z = 1.56). The size of the circles and squares is proportional to the membership probability. The HSC g, r, i composite image has a size of 0.05 deg and is centred on the background cluster.