One common theme is the 'opposites attract' concept. Given sakusa's quiet and clean - freak nature and atsumu's more energetic and sometimes messy personality, this contrast often forms the basis of their relationship in fanfictions. Another theme is their mutual growth. They help each other become better players and people in many stories.
" Rapunzel Maiden " was a fairy tale created by the Grimm Brothers in Germany. It told the story of a girl with magical hair who met a prince and lived happily together after suffering. In the story, a couple had never given birth. The wife saw the beautiful lettuce in the garden and longed to eat it. In order to satisfy his wife's wish, the husband secretly picked a handful of lettuce for his wife to eat. However, his wife's desire grew stronger and stronger. She became haggard, pale, and in pain. In the end, she was found by the witches and imprisoned in the tower. Later, when the prince passed by the garden, he heard the singing of Rapunzel. He climbed up the long hair and entered the tower to save her. In the end, they lived happily together. This story conveyed the principle of not stealing other people's things, not giving up halfway, and persisting would lead to victory.
One popular type might be the ones that focus on their rivalry turning into friendship and then something more. For example, there could be a fanfiction where they start off competing for a spot on the team but gradually realize they have a deeper connection. Another could be set in an AU (alternate universe) where they meet in a completely different context like at a music concert and their relationship blossoms from there.
Rapunzel in the real story is very brave. Despite being locked in a tower for years, she didn't lose hope and was able to face the challenges when the prince came and when the witch found out about their relationship.
There are many out there. 'Opposites Attract' is a really nice one. It delves deep into how sakusa's reserved nature and atsumu's more outgoing and flamboyant personality play off each other. The fanfiction does a great job of creating situations where they have to rely on each other, leading to a beautiful relationship development.
In the German original, Rapunzel is portrayed as a rather innocent and naïve girl. She has been locked in the tower for a long time, so she is somewhat sheltered. When the prince comes, she is easily charmed and falls in love quickly. Her long hair is not just a physical feature but also a symbol of her captivity and later, her connection to the outside world.
Some Tumblr blogs also post or recommend Haikyuu fanfictions. You can search for Haikyuu fanfic blogs and then specifically look for Sakusa x Atsumu stories on those blogs. The bloggers often give a little summary or their thoughts on the fics, which can be helpful in deciding if it's something you'd like to read.
Rapunzel is definitely not true. It belongs to the realm of fantasy and folklore. Tales like Rapunzel are often used to spark the imagination of children and adults alike, but they have no basis in reality.