Natsuki Subaru was a very lucky man. After dying so many times he finally managed to save everyone, he managed to restore Rem's name and memories and he helped Emilia acomplish her goal of freeing the elves. He was able to live a happy and peaceful life with Emilia, Rem, and Beatrice.
He was loved by them even though he knew that he didn't deserve it, he was a useless scumbag that had let them die over and over again. If he had been stronger and better then they wouldn't have died or suffered as much, he practically killed them himself with his weakness. He didn't understand why they would ever love scum like him, but he was happy that they did.
Subaru loved Emilia so much, she was his reason to live. She was the first person to help him in this world, she saved him in that alleyway and during the loops at the mansion she always was kind to him, when he was starting to go insane she gave him a lap pillow and saved him. She made him believe in himself and trust others. She was kind and selfless, even when she was hated by the world Emilia still tried to help everyone and didn't even ask for a thank you or any compensation. As long as Emilia was safe, Subaru could say that all of his suffering and pain was worth it.
Subaru loved Rem as much as he did Emilia. She risked her life for his useless self so many times. When he tried to run away like the useless coward he was, she convinced him to keep on going. When he hated himself, she loved him. When no one would believe him she did. When he did not even know who he was anymore, she told him to stand up. She saved him when he was all alone and about to go insane in Vollachia.
Subaru didn't love Beatrice in the same way that he did Rem and Emilia, but he still loved her. He was able to show her a side that he couldn't show others, she knew things about him that others didn't. She knew about his connection to the witch, something that would no doubt cause Rem and Emilia to hate him. She still trusted him even after he failed her so many times. She was his partner and they would always be together.
Subaru was a very lucky man, even though he was useless fool who could only die over and over again, he was still loved. He was married to both Rem and Emilia and he was so happy.
One day the Emilia camp decided to get together at Roswaal's mansion, everyone from the Emilia camp was there.
Subaru was talking with Garfiel and Otto when he heard a strange noise.
"Hmm, Roswaal! Yes! Yes!" It sounded like Emilia was moaning
"Hmm, Yes! Roswaal-Sama. Harder!" This time the voice sounded like Rem.
Subaru went to where the voices were and he found himself in front of a room.
He opened the door and was shocked to find Roswaal in bed with both Emilia and Rem!