Cultivating Immortality in the City Without Limits

Ten years ago, I read this book. The ending was about the last saint opening a harem in an infinite space, an assassin and a doctor getting together. The doctor received the Op-Op Fruit. Later, the assassin died, and the doctor performed an immortality surgery on him, reviving him, and they got together again.

It's really good, author, keep up the good work!

I thought it was really Battle Through the Heavens, but it's clearly the Main God!