Perhaps Yusuke would become consumed with revenge if Keiko's death was caused by someone or something malicious. He would use his demon powers to track down the culprit and seek justice. In the process, he might face difficult moral choices that further shape his character in this new, tragic situation.
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.
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.
Yusuke would likely become more withdrawn.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.
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.
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 be extremely angry. He would immediately start looking for Keiko. Yusuke is very protective of her, so he would drop whatever he was doing and go on a full - scale search. He might first try to find Hiei's usual hiding places in the demon world and question any demons he comes across.
You can try fanfiction.net. It has a large collection of various fanfictions, including those of Yusuke and Keiko.
Yes, there are quite a few. You can start by looking on fanfiction platforms like Archive of Our Own. Just search for 'yusuke and keiko love' and you'll find a variety of stories written by different authors with different takes on their relationship.
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 can be developed through shared experiences. For example, if they face a common enemy together. Yusuke's demon powers can be used to protect Keiko, which deepens their bond. Also, communication is key. Yusuke can open up to Keiko about his new life as a demon, and she can share her fears and concerns about his transformation.