Once upon a time in the city of Kobe, there was a girl and a boy. Both lived under abusive households, and the two swore an oath to be together until death. However, they are quickly separated, seemingly forever. That is, until a chance encounter reunites them three years later...

1000 years ago in the Heian Period, the human Princess Shizu and the oni Shuri (also known as Benkei) fell in love and married. When the princess died young, the oni turned to stone in his grief.

1000 years later in the modern day we meet high school girl Shizuko. On her 16th birthday, when she is old enough to marry, she is accosted by Shuri who has awakened from the stone and now claims to be her husband. It turns out that Shizuko is the reincarnation of Princess Shizu. Shizuko is overwhelmed and weirded out by all this. Shuri, meanwhile, declares his everlasting love for Shizuko and resolves to do everything in his power to make her love him again like she did in her past life.

Aika Asakura was about to jump the cliff, but she instead saved a cat. There she encounters Hotoka Houshido, a veterinarian that saved the cat's life. However, saving this little critter had unfortunately left her in debt, so he had arranged for her to work and live with him...

From MangaHelpers:
In this story set in the early 1920s, Tamahiko is the son of a wealthy family, but his life is changed forever when an accident cripples his right arm. No longer considered by his father as an heir, he is shuffled off into the country, to live out of sight. The teenage Tamahiko shuts himself in his new home, bitterly thinking of it as the place where he will die. One day, he learns that his father has 'bought' him a bride to take care of him, when the young teen girl named Yuzuki arrives at his door. She comes into his life like an innocent ray of sunshine, and Tamahiko's view of the world and his life starts changing bit-by-bit.