One common theme is the exploration of unrequited love. Sakura's love for Sasuke is well - known, and when he leaves her for Karin, it delves into the pain of unrequited love from Sakura's perspective. Another theme is the idea of choosing based on power and usefulness. As Karin has certain powers that can be of help to Sasuke, it shows a theme of practicality in relationships.
Love triangles are a very common theme. Sasuke is often at the center of the attention of both Sakura and Karin, which creates a lot of tension and drama.
There are fanfics like that. Sasuke might leave Sakura for Karin because of Karin's loyalty. Karin has shown unwavering loyalty to Sasuke throughout the series. She was willing to risk her life for him on multiple occasions. In contrast, Sasuke might think that Sakura's love is more of a childhood crush that she hasn't fully grown out of, and he may be drawn to Karin's more mature and selfless loyalty.
Karin could be heartbroken. She might initially be angry and feel betrayed, lashing out at Sasuke for choosing Sakura over her.
One common theme is unrequited love. Often, Sakura has deep feelings for Sasuke which are shown through the symbol of sakura leaves. Another theme is redemption. The sakura leaves can represent new beginnings and Sasuke's journey towards redemption. For example, Sakura might use the beauty of the sakura leaves to remind Sasuke of the good in his life.
Sakura might be heartbroken. She's been in love with Sasuke for so long. She could initially go into denial, thinking it's just a temporary thing. Then she might get angry and vow to prove herself to Sasuke, perhaps by becoming an even stronger ninja.
One possible reason in this fanfiction scenario could be that Sasuke feels a stronger connection to Karin on a spiritual or power - related level. Karin has unique abilities that might attract Sasuke more than Sakura's medical ninjutsu. Maybe he sees in Karin a kindred spirit in terms of their past traumas and the way they've had to fight to survive. Also, Karin has always been very devoted to Sasuke, and he might be drawn to that unwavering loyalty.
One possible reason could be his long - standing feelings for Sakura. Despite his journey and time with Karin, his original connection with Sakura might have resurfaced. Sasuke has known Sakura since they were young, and those early memories and emotions could have influenced his decision.
I don't have specific knowledge about the common themes in 'karin x sakura lemon fanfic' as it depends on the creativity of the writers. But friendship or adventure could be possible themes.
A common theme is redemption. Sasuke has a complex past, and many fanfics focus on how Sakura helps him find redemption and come back to the side of good. Another theme is love conquers all. Despite all the hardships and differences between them, their love is shown to be strong enough to overcome any obstacle.
The theme of sacrifice is quite common. Sakura has always been willing to sacrifice for Sasuke, and this is often highlighted in fanfics. Another theme is the power of second chances. Sasuke getting a second chance at life in the village and with Sakura is a frequent plot point. Also, the theme of healing. Both of them have emotional scars, and fanfics often deal with how they heal each other's wounds.