Takano could be developed by showing his growth from being a bit of a loner to opening up more because of Ritsu. For example, he starts to participate in more school group activities. Ritsu, on the other hand, can become more confident. Maybe he stands up to bullies in the school with Takano's support.
For Eren, he could start off as a bit of a rebel in high school. Maybe he's always getting into trouble for questioning the school's rules. But as he spends more time with Mikasa, he starts to see the importance of following some rules and also becomes more empathetic. Mikasa, on the other hand, can be developed as the quiet, studious type who slowly comes out of her shell because of Eren's influence.
Ash could be developed by showing his growth not just as a Pokémon trainer but also as a student. He might struggle with academics but use his Pokémon training skills to find unique ways to study. For example, he could use his Pikachu to remember facts by associating them with Pikachu's electric attacks. Serena, on the other hand, could be developed by exploring her dreams outside of Pokémon contests. Maybe she discovers a new talent in high school, like painting Pokémon, which also deepens her connection with Ash as he encourages her new hobby.
You can try some popular fanfiction websites like Archive of Our Own (AO3). It has a large collection of various fanfictions, including those of takano x ritsu. Just search for the relevant tags and you might find some great lemon fanfictions there.
In many fanfics, the relationship between Takano and Ritsu is often intense. There's a lot of emotional turmoil as they navigate their past and present feelings for each other. Takano is usually depicted as dominant, while Ritsu is more on the shy and flustered side.
For Ash, he could develop by learning more about academics in the high school setting. He's always been focused on Pokemon battles, but in high school, he might struggle with subjects like math or history. Serena can help him study, and this can show his growth in being more well - rounded. Also, his leadership skills in Pokemon battles can translate to leading school projects or teams.
For Naruto, his character could develop by becoming more confident in his academic abilities. In high school, he might struggle at first but with Sakura's help, he could improve. This would make him more self - assured. For Sakura, she could develop by learning to be more open - minded. Maybe Naruto introduces her to new hobbies or ways of thinking that she wouldn't have considered before.
Sasuke could be developed as a brooding and mysterious vampire. He might be struggling with his vampire nature, like the urge to feed on his classmates. Sakura could be the one who helps him come to terms with it. For example, she could show him that there are ways to control his thirst without harming others.
Characters like Annabeth could be developed by exploring her jealousy or concern when Percy is spending so much time at Ares High School. She might try to infiltrate the school in some way to keep an eye on him. And for the Ares - influenced characters, you can show their internal conflict between following Ares' brutal ways and their own sense of right and wrong as they interact more with Percy and his friends.
One popular takano x ritsu lemon fanfiction might be 'Love's Unspoken Words'. It delves deep into their relationship with some really sweet and intense moments. Another could be 'Hidden Desires' which shows a more complex side of their connection.
In a high school setting, Yoh's character could develop by becoming more responsible. For example, he might take on leadership roles in school clubs related to the spirit world. This would force him to be more organized and decisive, which are traits he doesn't always show. Anna, on the other hand, could learn to be more open - minded. She could start to see the value in Yoh's more relaxed approach to things when they deal with high school problems like handling difficult teachers or mean classmates.