Both are about mystery, you'll realize soon enough they are similar, cliffhangers and plot-twist in every episode.

Both share the same story line, in Himitsu the mother died and then come back in her daughter's body.

Both drama are about secret that lies into dysfuntional families and how they overcome their difficulties

They both deal about extra marital affairs. Utsukushii rinjin is more intense and thrilling.

They both deal with housewife being suspicious about their husband. Yakou Kanransha is more about the secret that lies in each family of the same neighborhood and how they deal with them

Both are about bullying. One happens in school and the other in a company.

Both dramas share the same feeling. Students are isolated from the outside world and one of them is a psycopath.

Both are about a families who seem to be normal from the outside, but in fact they have dark secret.