Another theme is sacrifice. Yusuke has sacrificed a lot in his life, and Keiko is often by his side. Fanfics may show how they both make sacrifices for each other and for their relationship. For example, Yusuke might sacrifice his time or safety to protect Keiko, and she might sacrifice her own desires for Yusuke's well - being.
Growth is also a prevalent theme. Yusuke goes through a lot of personal growth in the original story, and Keiko is part of that journey. Fanfics often depict how they grow together as individuals and as a couple. They learn from each other and become better versions of themselves because of their relationship.
Growth is another theme. Yusuke often goes through a lot of changes, and Keiko is there. Fanfictions might show how they both grow as individuals and as a couple in relation to those changes. For example, Yusuke becoming more responsible and Keiko being more understanding.
Yusuke would likely become more withdrawn. He was always a bit of a rough - around - the - edges character, but Keiko's death would make him more somber. He might lose his sense of humor that he sometimes showed around her.
A common theme is friendship. Their bond as friends is often explored and how it can develop into something deeper. For example, in many fics, they start as classmates or teammates and gradually realize they have stronger feelings for each other.
Another common theme is loyalty. They are both loyal to each other in the original, and fanfics build on that, showing how their loyalty can be a foundation for a closer relationship. For example, in many fanfics, they stand by each other in difficult situations that test their bond.
One great 'yusuke x keiko fanfic' could be 'The Unspoken Bond' which delves deep into their relationship. It shows how Yusuke's rough edges are softened by Keiko's gentle nature.
One common theme is the exploration of their hidden desires. Since the 'lemon' aspect often implies a more sensual side, it could be about Yusuke and Keiko exploring their physical attraction that they may have suppressed in the original story. Another theme could be the intensification of their emotional bond. Through various situations in the fanfiction, their love and understanding for each other can grow deeper.
Yusuke might cope by throwing himself into his work as a spirit detective. He could try to distract himself from the pain of losing Keiko by taking on more and more dangerous cases. This would be his way of running away from his emotions at first.
There's this fanfic called 'Together Always' which is really interesting. It delves into how Yusuke and Keiko handle the challenges in their relationship. It shows Yusuke's growth as a character in the context of his love for Keiko. Keiko, on the other hand, is depicted as being very supportive of Yusuke's journey.
To write this fanfic, you need to understand the characters well. Yusuke is tough on the outside but has a soft heart. Keiko is strong - willed and intelligent. Use these traits in the story. For instance, when they face difficulties during the pregnancy, Yusuke might want to solve them with his fists at first, but Keiko would remind him to think rationally. Also, add some cute moments, like Yusuke feeling the baby kick for the first time.
You can try fanfiction.net. It has a large collection of various fanfictions, including those of Yusuke and Keiko.