A Nun and Her Lustful Knights

A holy nun, suddenly married...?! And now she needs to give birth to a heir?! Mari was staying in a monastery up until a butler by the name of Suzaki appears with the task of bringing her to his lord, Seishiro. Mari is now invited to live on his estate as this lord owes a great debt to her grandmother... after talking with lord Seishiro it comes to be that even though he is closer in age to her grandfather, they are somehow to be married...! However, Lord Seishiro states, "You will sleep with the man I choose, and the child you bear shall become my heir." What?!?!