Nora to Oujo to Noraneko Heart

Nora lives together in Sakuragabuchi with Shachi, a girl younger than him whom his mother had adopted. After his mother’s passing, they were able to grow up just fine with the support of those around them. Shachi loves Nora very much, and wakes up him every day while straddling him in bed. Then they head to school and enjoy their time with their friends, including their childhood friend and discipline committee head Michi, and his cheerful gyaru-like kouhai Yuuki.
One day, Nora came upon a girl named Patricia in a park on his way to school. She was a Princess of the Underworld and she came to the world of the living on her mother’s orders to destroy everything and remind humans of death. However, the life energies were too strong for her and she was overwhelmed by it. Nora took care of her while she was feeling ill, and she fell in love with him as a result. She asked him to explain the ‘mysteries of life’, but why does that include reading porn books...!?