In the manga, Tanjiro and Kanao don't end up getting married. The story focuses more on their battles and character development rather than romantic pairings.
Well, it could be about a BTS member accidentally running into a gymnast YN at a sports event. Maybe they get to know each other gradually and BTS is inspired by YN's dedication in gymnastics. It could also involve YN getting a chance to perform at one of BTS's concerts, creating a unique and exciting plot.
One great tanjiro and kanao fanfiction could be where they go on a journey together to find a rare herb for an ailing comrade. In this story, their relationship deepens as they face various obstacles in the forest.
One way is through a charity event. BTS is often involved in charity work, and YN could be performing at a gymnastics - related charity event. They meet there and start interacting. Another way could be if YN is a back - up dancer for another K - pop group and during a big K - pop concert, BTS and YN cross paths.
Tanjiro and Kanao's love is a slow - burning and sweet one. They first meet as comrades in the fight against demons. Tanjiro's kind heart and strong will gradually draw Kanao out of her shell. Kanao, who was initially rather reserved, starts to open up more because of Tanjiro. Their relationship develops as they face numerous challenges together, and their mutual respect and growing affection for each other are heartwarming to watch in the series.
It develops gradually. At first, they are just fellow Demon Slayers. But as they spend more time together, they start to understand each other better. Tanjiro's unwavering determination and his ability to see the good in everyone, including Kanao, make her fall for him. Kanao also shows her loyalty and care towards Tanjiro, which deepens their connection.
You can start by looking on fanfiction platforms like Archive of Our Own (AO3). It has a large collection of fanfictions, and you can search specifically for Tanjiro and Kanao stories. Another option is Fanfiction.net, though the interface might be a bit less user - friendly in terms of filtering. Some Tumblr blogs also share and recommend good fanfictions in this category.