The slice - of - life genre also works well. A fanfiction where we see their daily lives in the village, Rock Lee training hard as usual and Sakura working in the hospital, and then little moments where their paths cross in a more personal way. Maybe Rock Lee brings Sakura some flowers from his training ground as a friendly gesture and these small interactions build up over time.
There could be a fanfiction where Sakura, being a medical ninja, has to save Rock Lee from a near - fatal injury. This situation then leads to a series of events where Rock Lee realizes his true feelings for Sakura and they start a relationship that is full of mutual respect and support.
One interesting storyline could be a story where Rock Lee tries to impress Sakura with his new and improved ninja skills. He shows off his unique taijutsu moves in hopes of winning her heart. Another could be a fanfiction where Sakura realizes Rock Lee's deep and unwavering loyalty and starts to see him in a new light. For example, when the village is in danger, Rock Lee is always the first to volunteer to protect it and Sakura, which makes her think differently about him.
A possible plot idea is that Sakura discovers a hidden side of Rock Lee. Maybe she stumbles upon his love for painting or some other artistic hobby that he has kept secret because he thought it might seem un - ninja - like. This could lead to a deeper understanding between them and a new level of friendship. Or perhaps there's a plot where Rock Lee gets injured severely, and Sakura has to use all her medical knowledge to save him. During his recovery, they have long conversations that make them realize how much they have in common and respect each other more.
Their relationship could develop through mutual respect for each other's skills. Rock Lee admires Sakura's intelligence and medical abilities, while Sakura respects Lee's determination and physical strength. They could start training together, with Lee teaching Sakura some of his physical combat techniques and Sakura helping Lee with his studies or knowledge about herbs and medicine. This exchange of skills would bring them closer as friends.
Rock Lee is a character who overcomes his lack of natural talent in ninjutsu through sheer hard work and determination. His character is defined by his loyalty to his friends and his village. Tenten, being a weapon - specialist, is not just about fighting. She also has a side to her where she is a good friend. In this fanfic, they are the central figures around which the story is likely to revolve.
Overcoming past traumas is also a theme. Gaara has his past with being a Jinchuriki and Rock Lee has his insecurities about not being able to use ninjutsu. In fanfiction, they often help each other heal and grow from these past issues. And of course, the theme of loyalty. They show loyalty to each other in different situations which deepens their connection.
One common theme is mutual growth. Since they are both ninjas, stories often show how they help each other improve their skills. Another theme is unspoken love. There's often a sense of a relationship that's there but not fully expressed. And loyalty is also a big theme. They are loyal to their village and to each other in many of these fanfics.
Another concept could be Rock Lee traveling to a time before the founding of the Hidden Leaf Village. He could witness the origin of ninja clans and their unique fighting styles. This would give him a new perspective on his own fighting style and he could incorporate some of the ancient techniques into his taijutsu.
One possible storyline could be that Rock Lee and Tenten go on a mission together and during the mission, they face various challenges that strengthen their bond. For example, they might have to protect a village from a group of bandits. Rock Lee's physical strength and Tenten's weapon skills would complement each other, and through this experience, they develop a deeper understanding and friendship.