In a fanfiction, Mosquito Girl could develop a grudging respect for Saitama. After being defeated by him, she realizes that there are beings far more powerful than her. And Saitama, on the other hand, might start to see Mosquito Girl as more than just a villain. Maybe he discovers that she has some good qualities, like her tenacity. So their relationship could shift from pure enmity to a more complex dynamic of mutual understanding.
Saitama might be really frustrated with Mosquito Girl. Since he can defeat most powerful foes with one punch, but a mosquito girl would be a different kind of annoyance. She could be constantly buzzing around and trying to bite him, and Saitama would probably just try to swat her away like a normal mosquito at first. But when he realizes she's a 'villain' in her own right, he might just give her one quick punch to end the nuisance.
In a romantic setting, their relationship might start off slowly. Saitama would probably be oblivious to Tatsumaki's initial feelings. Tatsumaki, being the proud and strong - willed character she is, would have a hard time expressing her emotions directly. It could start with small acts of kindness from Tatsumaki towards Saitama, like using her powers to fix his apartment when it gets destroyed in a fight. Saitama might just think it's a normal thing at first.
In One Punch Man fanfiction, Mosquito Girl can be a really interesting character to explore. Some fanfictions might focus on her backstory, like how she became the way she is. Maybe she had a difficult past that led to her transformation. In these stories, authors can give her more depth than what we see in the original manga or anime.
In fanfiction, Mosquito Girl can be characterized in various ways. One way is to make her more sympathetic. Maybe she was forced into her evil ways. So, she could be written as a victim of circumstances.
Some writers develop their relationship through shared experiences. Let's say they both get transported to a strange dimension. In this new and dangerous place, they have to depend on each other. Saitama might use his strength to protect Tatsumaki from physical threats, while Tatsumaki uses her psychic powers to navigate and solve puzzles. Through these shared experiences, a bond forms. They start to respect each other's abilities and personalities more, which could lead to a deeper connection, be it friendship or love.
One way to develop Mosquito Girl further is to give her more complex emotions. Instead of just being a one - dimensional villain, show her moments of doubt, fear, or even kindness. For example, she might spare a small child during an attack because it reminds her of a past memory. Another aspect could be exploring her powers in more depth. Maybe she has some hidden abilities that are revealed as the fanfiction progresses.
Saitama would be shocked at first. He's used to Genos being around, always eager to learn from him. He might stand there in disbelief for a while.
Genos would probably be even more in awe of Saitama. He already idolizes him, but with Saitama being S - Class, Genos might see him as even more untouchable. He could become more protective of Saitama's new status, trying to fend off any detractors or those who might try to take advantage of Saitama.
Their relationship can be developed by having them face more personal challenges together. For instance, if Genos' family past is explored and Saitama helps him come to terms with it. Or they could have a fight over a difference in opinion, like how to handle a new, extremely powerful villain. After the fight, they realize how much they mean to each other and their bond grows stronger.
One way is to explore his life before he became a hero. Maybe he had a normal job and was constantly frustrated with the mundanity of it. This could have been the catalyst for his intense training.