The theme of acceptance is key. They have to accept their feelings for each other despite the challenges they face from their friends, family, and the different natures of their existences. Their journey towards acceptance is often a central part of these fanfictions.
One common theme is the exploration of forbidden love. Since Castiel is an angel and Dean is a human, their relationship often goes against the norms of both their worlds. Another theme is sacrifice. They are often willing to sacrifice a great deal for each other.
Self - discovery is also a prevalent theme. Through their relationship, both Castiel and Dean learn more about themselves and their capabilities of love. The theme of redemption can also be found. Their love can be seen as a way for them to redeem their past mistakes or shortcomings.
One common theme is friendship. Their bond, whether it's a platonic friendship or something more, is often explored. Writers like to show how they support each other through tough times.
One popular 'dean kisses castiel fanfiction' is 'Heaven's Embrace'. It beautifully depicts their relationship with a lot of emotional depth. The author does a great job of building up the tension before the kiss scene.
A common theme is friendship. Often, the stories focus on how the reader becomes friends with Dean and Castiel. Another theme is adventure. Since they are hunters in the Supernatural world, they go on many adventures together with the reader. For instance, they might go on a quest to find a powerful artifact.
Love and acceptance are also very common themes. Dean may struggle at first with his feelings for fem Castiel, but eventually comes to accept and love her for who she is. There's also the theme of power. How does fem Castiel's power change or stay the same in relation to Dean? And how do they use their combined powers in different situations, like during hunts or facing off against supernatural enemies.
One common theme is redemption. After Castiel hurts Dean, he often tries to redeem himself, which shows the depth of his love and friendship for Dean.
Another theme is the idea of identity. How does Castiel's female form change her perception of herself and how does Dean view her differently? It can lead to stories that are centered around self - discovery and acceptance. In some fanfictions, Castiel struggles with being in a female body and Dean helps her come to terms with it, which is a really interesting take on their relationship.
Another theme is the struggle between their different natures. Castiel being an angel and Dean being a human hunter. This creates a lot of internal and external conflict in the stories, like in 'The Clash of Worlds' fanfiction where they have to overcome their differences to be together.
Fanfiction.net is also a good place. There are many talented writers who contribute to this genre. Just use the search function and type in 'dean kisses castiel' to find relevant stories. However, the interface might be a bit more cluttered compared to AO3.
A popular one is 'The Kiss of the Seraph'. It shows how Castiel overcomes his angelic inhibitions to express his love for Dean through a kiss. The story has a great deal of character development and the relationship between the two is portrayed in a very engaging way.
One common theme is loyalty. They are always there for each other in most fanfics, no matter what the situation is. Another theme is the struggle between the human and the supernatural world as Castiel is an angel and Dean is a human hunter.