As it says from the synopsis, ML really did fell in love with MC on first sight. Reason being--- because of her soul (literally). ML actually knew MC from her previous life. He was one of her patients. Due to the scheming of his younger brother, he ended up being wasted and was removed from being the heir of his family. In the hospital, he was disgusted with the pitiful look people gave him whenever they came to see him. That was-- until he met MC. Unlike the others, MC looked at him with clear eyes without a trace of pity. After getting to know her, he requested for her to be his primary doctor. They spent their days together like close friends, and eventually one day, she ended up getting drunk. He knows she normally doesn't drink, but then he found out it was because someone who was like a brother to her from the orphanage she grew up in, died from illness. ML then suggested for her to take a break and to go back home, so she complied. Little did they know, an airplane accident would occur. After her disappearance, ML was heartbroken and realized his feelings for her. He spent years and resources trying to find her body, but in the end, was unable to.
Eventually, he then gained a system. The system was called small seven (Xiao Qi). According to ML, he lived over thousands of lives (that didn't involved love), and had to gain over 1 billion points in order to revive MC. In the last world he was assigned to (the novel world where he and MC are currently in), he would've never imagined that he'd encountered MC's soul again. As a result of this, he told small seven he no longer desired to have his wish granted of going back to his world fully cured and having MC revived again. Instead, he wished to stay in this world until the very end to be with MC. if he had left after completing his task, the world would of collapsed.
We also get a glimpse of how MC thought of past!ML from her previous life, but unlike him, she had no idea ML was actually him. MC had this feeling that past!ML liked her, but because he never said anything nor looked like he would, she never mentioned it. Because of their relationship, it actually inspired her to write a story called "Sunflower". The story was about a couple failing to be together in the end. When the male lead proposed to the female lead, she declined his proposal. The more he persisted on being with her, the more she closed her heart. Even though his actions did move her, in the end, what she felt for him wasn't love. Therefore, she couldn't be with him. Basically, this story based on her and past!ML.As a pair of men and women sat on a double rocking chair in the courtyard, MC leaned on ML's shoulder and whispered to him to not be sad. She expected that this day would come. With being with him for so many years, she's content. After coming to this world at the age of 22, she had been entangled with him for the rest of her life. For the entire period of 86 years, she was accompanied by this sentence. ML smiled and used his arm to take the shoulder of the person around him. MC sighs and says how she regrets being unable to have a child with him. ML comments how it's his fault. During the pre-martial examination, the doctor told them that his sperm survival rate is very low, making it difficult for MC to become pregnant. After so many years, they were never able to have children.
ML then recalled a conversation he had with small seven. It turns out he took a dan to make it so that he couldn't have children. How could two souls from the real world possible conceive a heir in a world that's real and imaginary? Instead of getting her into impossible hopes and despair, it's better to sever the possibility from the beginning. She'd be more at ease if he took matters into his own hands.
Hugging MC close to him, he tells her that things are just fine with only him and her. MC smiled and agreed. Putting her hair behind her ear, she stared at the cat by her feet. She tells him to take care of Alan, but also take care of himself, she continues telling him where what clothes were, to water the flowers his students sent, where the secret key to the wine in the drawers were, and because he's still in good health, if he isn't doing anything, walk their cat.. Eventually, her voice drifted into the wind. ML gradually embraced the person who no longer spoke into his arms, lowered his head, then kissed her between her eyebrows tenderly. The time gradually became stagnated. From the distant edge of the unknown world, it slowly started to decay. The man slightly hooked his lips. With some effort, he lifted his arm and tightly grasp the person in his bosom. Nesting his chin onto her shoulder, he closed his eyes with a peace of mind.
The ending is sad to be honest and I get that it’s one of a kind happy ending but I’m still not satisfied as I want them to go back to their original world and continue their lives together I’m gonna miss them,