Yusuke would also become more empathetic towards others who have lost loved ones. Before, he might have been a bit callous in some ways, but now he understands the true pain of loss. This could lead him to be more involved in helping those in similar situations, while still being on his mission to either avenge Keiko or find a way to bring her back.
He would become more reckless in his battles. Without Keiko to ground him, he may not care as much about his own safety. He could be more willing to take on extremely dangerous foes without proper planning, as his main reason for self - preservation (being with Keiko) is gone.
Yusuke would likely become more withdrawn.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.
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.
One possible plot could be that Keiko is caught in the crossfire of a demon battle that Yusuke is involved in. Yusuke, being a spirit detective, has many enemies. Maybe a powerful demon targets Keiko to get back at Yusuke. After her death, Yusuke could go into a deep state of despair and vow revenge. He might journey to the spirit world to find a way to bring her back, facing numerous challenges along the way.
You can try fanfiction.net. It has a large collection of various fanfictions, including those of Yusuke and Keiko.
One way the story could develop is that Yusuke goes into a deep state of grief and denial at first. He might start to isolate himself from his friends and the spirit world as well. He could be haunted by memories of Keiko and constantly wonder if there was something he could have done to prevent her death.
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.
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.
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.
The relationship could develop in a rather unique way. Maybe Yusuke saves Keiko from a life - threatening situation, which makes Keiko see him in a new light. Yusuke, on the other hand, is drawn to Keiko's purity and kindness. As they spend more time together, Yusuke starts to change for the better because of Keiko's influence. Their relationship might be full of misunderstandings at first, but as they communicate more, they grow closer and closer, eventually falling in love.
There are also some niche fandom - specific forums where fans might share their own written Yusuke and Keiko fanfictions. These can be a bit harder to find, but if you search around in relevant anime or manga forums, you might stumble upon some hidden gems that haven't made it to the bigger fanfiction platforms yet.