One common theme could be his backstory. Writers might explore his past experiences to give more depth to his character. For example, his upbringing and how it shaped him into who he is.
Well, without more context, it's hard to say exactly. Maybe Jin Choi had a sad story related to his career. Perhaps he was passed over for promotions repeatedly, or faced discrimination at work which led to a series of sad events in his professional life.
Since we don't have much information, 'choi minhwan first story' could cover a wide range of things. Maybe it's about Choi Minhwan's first encounter with a certain person who had a great impact on his life. It could also be related to his first attempt at a hobby or passion that later became an important part of his identity. It really depends on who Choi Minhwan is and what context this 'first story' is being told in.
Adventure is another one. They could be on a journey to discover something, like a hidden treasure or a lost power. This makes the story exciting and full of action.
Friendship is a very common theme. Many fanfics explore how Minho and Taemin have a special bond as friends and colleagues in the entertainment industry.
Power and influence are sometimes explored in Choi Young Do fanfics. Given his status in the original story, some fanfics play around with how he uses or misuses his power. Also, forgiveness is a common theme. Other characters may have to forgive him for his past actions, or he may have to forgive others. It makes for some very emotional and engaging storylines.
One common theme is redemption. Since Choi Young Do has a complex character in the original work, many fanfictions focus on him redeeming himself from his past wrongdoings. Another theme is love. Whether it's a romantic love or a platonic love for his friends, it often plays a big role in these stories.
One great Boo Seungkwan and Choi Yena fanfic is 'The Unlikely Bond'. It's a story that beautifully weaves their personalities together. It shows how they might interact in a fictional high - school setting, with Seungkwan's humor and Yena's spunk creating some really interesting and heart - warming scenes.
One common theme is friendship. Often, the fan fictions will show San forming deep and meaningful friendships with other characters, whether they are fellow idols or original characters created for the story.