Kirihara Ryouji and Karasawa Yukiho are bound by tragic fate from a young age to become partners in crime. A moving story of the lengths to which one would go in love, to protect another, even at death's cost.
1) They share the same scriptwriter, lead actors and singers
2) The way to look at past and future of the lead actors are shared. The girl/woman never want to regret for her past but the boy/man is deeply attracted by his past.
3) Both drama are pure love, both their colour are exactly opposite. Sekai is white pure love and Byakyyakou is dark pure love.