One common theme is the exploration of their different personalities coming together. Tanjiro is very kind - hearted and Shinobu has a more complex, somewhat mysterious nature. Fanfics often show how they bridge that gap.
A frequent theme is secrecy. Shinobu's yandere feelings are often something she tries to hide from others, especially from Tanjiro at first. Also, the theme of protection can be seen. Shinobu may see her yandere actions as a way to protect Tanjiro from other threats, real or imagined. This can lead to some interesting plot twists as Tanjiro may not always understand her motives.
Another theme is mentorship. Shinobu, being more experienced, often acts as a mentor to Tanjiro. She imparts her knowledge about demons and fighting techniques. This is seen in quite a few fanfictions where Tanjiro looks up to Shinobu for guidance.
One common theme is the growth of their relationship. It often starts from a simple acquaintance and develops into a deep emotional bond. For example, they might start as comrades in the fight against demons and gradually fall in love.
One common theme is the exploration of their contrasting personalities. Shinobu is often seen as more light - hearted and talkative, while Giyuu is quiet and reserved. Fanfictions usually play with how these differences can either create friction or bring them closer together.
The themes usually include unspoken love. Since both characters are not very vocal about their feelings in the original story, fanfictions often explore the idea of them having deep, unspoken emotions for each other. Also, there's the theme of support. They support each other in battles against demons, and this aspect is often elaborated on in fanfictions, like how Shinobu's medical knowledge helps Giyuu when he's injured.
One common theme is the exploration of their complex relationship. Given Shinobu's vampiric nature and Araragi's human - turned - vampire nature in a way, their relationship is full of power dynamics, loyalty, and a strange form of mutual dependence.
One great 'yandere Shinobu x Tanjiro fanfiction' is 'Shinobu's Obsession'. It really delves into Shinobu's yandere tendencies towards Tanjiro. The story shows how Shinobu's feelings start to cross the line from normal admiration to an all - consuming obsession. It's a really interesting read if you like this kind of pairing.
Another great one is 'Tanjiro and Shinobu's Journey'. In this, they go on a journey together that tests their relationship. It shows how they support each other through tough times, and it's full of action and emotional moments that make it an engaging read.
Protection is a common theme. Tanjiro is always looking out for Nezuko, whether it's from other demons or humans who fear her. Another theme is loyalty. Nezuko's loyalty to Tanjiro is unshakable and this is often explored in fanfics.
Love and friendship are very common themes. The fanfics often explore how the reader and Tanjiro develop a deep bond of love or friendship. Another common theme is adventure. Since Tanjiro is on a journey in the original story, many fanfics incorporate the reader into his adventures.