The Immortal Lord's Plan to Raise a Demoness

What? The male lead dies not long after he shows up?

Huh? They find a stand-in for the male lead, and he dies too?

What? She tries to kill herself, but an Immortal Lord saves her?

Immortal Lord: I saved you. How do you plan to thank me?

Female Lead: This humble woman will fast and bathe, then burn incense for the Immortal Lord every day, so that your offerings never cease!

Immortal Lord: I can teach you a way to keep my "lineage" going without all that smoke and incense...