Well, there are fanfictions where the OC has a unique backstory. For example, an OC who was once a part of a circus troupe and has acrobatic skills. When she meets Mako, he's initially skeptical of her but as they get involved in the Avatar's adventures, he comes to admire her tenacity. Some fanfictions focus on the romantic aspect right from the start, with Mako being instantly attracted to the OC's kind heart and beauty.
The 'lemon' aspect might be a bit hard to come by in a clean way as it often involves inappropriate content. But for normal Korra and Mako fanfictions, you could also try FanFiction.net. Some stories there might show their relationship developing, their adventures together, and how they support each other, which can be really interesting to read.
Archive of Our Own is a great place to start. It has a large collection of fanfictions, and you can easily filter out any inappropriate content. Just search for Korra and Mako, and you'll get a variety of stories exploring their relationship, from friendship to romance, all within the boundaries of a proper and respectful narrative.
They would probably raise their baby with a strong sense of justice. Korra, being the Avatar, would instill values of protecting the weak and upholding the balance of the world. Mako would teach the baby about the importance of family and loyalty. They might also encourage the baby to explore different bending techniques from a young age.
When writing a 'Legend of Korra Mako x OC' fanfiction, it's important to know the 'Legend of Korra' universe well. Research the different cultures, the political situation, and the technology. For your OC, give them a unique voice. If they're from a different nation, they might have an accent or use certain phrases. In terms of the relationship with Mako, create conflict and tension. It could be something as simple as Mako being too focused on his work as a police officer and the OC feeling neglected. Resolve these issues gradually as the story unfolds to make it a compelling read.
In fanfiction, their baby could be a powerful bender. Since Korra is the Avatar, the baby might inherit her strong connection to the elements. Maybe it would grow up to be a great hero, using its bending skills to protect the world like its parents did. It could also have a unique personality, a blend of Korra's headstrong nature and Mako's more reserved side.
Love is a big emotion. Even if it's just the start of their romantic journey, there's an underlying love that has been growing. There could also be a sense of relief, like they've finally let their true feelings show after holding back for so long. They might feel a bit giddy and happy, like they're on top of the world in that moment.
Perhaps they are having a quiet moment alone, like on a balcony overlooking the city at night. The stars are out, and there's a gentle breeze. They start talking about their feelings for each other, and before they know it, their lips meet in a soft, tender first kiss.
Well, there's the theme of trust - building. Given their different backgrounds and past experiences, fanfics often focus on how they gradually learn to trust each other completely. Also, the theme of family - how they become a family of their own, either through adoption or just creating a strong bond that feels like family, is quite common in mako x asami fanfic.
Yes, there are quite a few. You can start by checking fanfiction websites like Archive of Our Own. There are many talented writers in the fandom who create interesting stories about Mako and Asami.