Both have sadomasochist narcissist male protagonist. Physical - Domestic Abuse.

ON Song Huajai Nee Puea Tur

A businessman loses his memory and becomes someone who is the complete opposite of his former self and only remembers a woman and someone who looks like her, this involves past life memories

ON HJM Main lead has got dissociative identity disorder, he is also a chaebol, Main lady who's trying to save his circus in the theme park finds herself falling for both of personalities of the the main lead.

ON KMHM A chaebol suffers memory lapses and he has got personality disorder, he has got 7 personalities, a first-year psychiatric resident, to tries to helps him secretly, but she eventually falls in love with one of his personalities.

ON Song Huajai Nee Puea Tur

A businessman loses his memory and becomes someone who is the complete opposite of his former self and only remembers a woman and someone who looks like her, this involves past life memories

The plot is quite similar based on revenge and how the guy falls in love to the lady who he thinks killed his fiance.

It involves unrequited love story of parents and how their children fall in love in the present day finding their own happiness, also trying their best for their parents love...

Both girls fell pregnant after a one night stand, they both have to sacrifice to raise their kids.

Both male protagonists have lost their Crown Princess at the beginning of the drama, there is no time travel, but it is an historical romance

Both male protagonist are from past, it involves time travel, love and mystery

Both has Time Travel.. On both one of the couple is from an old era, On Rooftop Prince he is from Joseon Era, On Scarlet Heart modern girl travels back to Goryeo Era. Both has got great love story