A possible plot element could be a mystery that Tokaku and Haru have to solve together. This would play on the 'riddle' aspect of the original 'akuma no riddle' concept.
Another plot element might be a conflict within their relationship. Maybe there are misunderstandings or external factors trying to drive them apart, and they have to overcome these obstacles.
There could also be a plot element where Tokaku and Haru are on a journey of self - discovery, and their relationship evolves as they learn more about themselves. For instance, Haru might help Tokaku open up more, and in the process, they both grow as characters.
The fanfic might focus on the unique dynamics between Tokaku and Haru. For example, it could show how their personalities, one being more reserved perhaps (Tokaku) and the other more open (Haru), complement each other. It may also explore their shared experiences and how those shape their relationship within the story.
Tokaku is often portrayed as strong and protective. Her assassin - like skills make her a formidable character. But in fanfiction, her softer side for Haru is also a great trait. She is loyal and will do anything to keep Haru safe.
One idea could be that Tokaku and Haru go on a journey outside the school setting. They encounter various challenges that test their relationship and loyalty to each other. Maybe they have to deal with an enemy from Tokaku's past who is trying to harm Haru.
The unique dynamic between tokaku and haru can make tokaku x haru lemon fanfic interesting. Their individual personalities, with tokaku's mysteriousness and haru's own charm, can create an engaging relationship in the fanfic.
There could be a tokaku x haru fanfic that delves into their relationship development. For example, it starts from their first encounter, showing how their initial impressions gradually change as they spend more time together. They might find common interests and values that draw them closer, and the story could beautifully portray their emotional journey.
You can try looking on some popular fanfiction websites like Archive of Our Own. There are often a large number of fanfics from various fandoms, and you may be able to find tokaku x haru fanfic there.
One possible plot could be that Isuke and Haruki start off as rivals in the dangerous world of Akuma no Riddle. They might be competing for a certain goal or mission. As they interact more, they gradually discover they have more in common than they thought. Their relationship then evolves from rivalry to friendship and perhaps something more romantic as they face various challenges together.
I'm sorry, but I don't have specific tokaku x haru lemon fanfic to recommend directly. You can try searching on fanfic platforms like Archive of Our Own (AO3). They usually have a wide range of fan - made stories about various pairings.
A plot idea could be to create an alternate universe where the assassination game has different rules. Maybe instead of one - on - one assassinations, it becomes a team - based competition. This would change the dynamics between the characters completely.
Isuke could start as a very guarded character, but through interactions with Haruki, become more open and trusting. Haruki, on the other hand, might become more patient and understanding. For instance, if Isuke has trust issues due to past experiences, Haruki's kindness could slowly break down those walls, and Isuke would learn to be more vulnerable.