Both comment on the subject of sincerity and hypocrisy in the era of social network, especially Twitter.

Both are about children who witness the cruel death of people they love, and who promise to avenge them once they grow up.

Those two dramas...taste the same, I should say.

In Ouroboros, two childhood friends choose different paths to avenge a loved one: one a path of light, the other a path of darkness. They are compaired to an Ouroboros, two dragons biting each other's tail, symbol of eternity and harmony of light and darkness.

In Orthros no Inu, two men are connected by a mysterious bond: one is a good man cursed with the power to kill by one touch, the other is a criminal blessed with the power to heal with one touch. They are compared to Orthros Dog, a two faced dog, one good, one evil, bound together by destiny.

Basically the same drama, only one is supernatural oriented with a touch of crime themes and the other is full-on romance but with a gender-bending/sexuallity questioning theme instead.

Other than that, the atmosphere and setting, the cast and the dynamic between the characters are definitely similar.

So If you like the romance in one, you'll like the romance on the other.

Both have great actors and interesting stories that will make you both cry and laugh.

Both dramas have this old school - but effective - Lois Lane &Clark Kent/Superman relationship between the leads.

Also, the Female Lead is the same in both dramas, so you can see the improvement of the actress.