A common trope could be the 'fashion contrast'. Since the tall girl has a different body type, she might have a unique fashion sense that contrasts with the male reader. This can lead to interesting interactions as the male reader might be in awe of her style or they might have cute arguments about what to wear for different occasions. Also, the 'height - based insecurities' trope can be explored. The male reader may initially be insecure about his height compared to the tall girl, but as the story progresses, he learns to embrace it and sees it as an advantage in their relationship.
One popular trope is the 'gentle giantess' where the tall girl is physically imposing but has a soft and caring nature towards the male reader. Another is the 'protective tall girl' who uses her size to shield the male reader from harm. And then there's the 'awkward size difference' trope where their different sizes lead to humorous and endearing situations, like the male reader having to stand on tiptoes for a kiss or the tall girl accidentally knocking things over because of her height.
The size difference can create tension in the story when it comes to physical proximity. For instance, the male reader might be hesitant to get too close to the tall girl because of her imposing size, creating a palpable sexual or emotional tension.
One common trope is the 'Powerful Protector' where the male reader character becomes a strong figure to protect the DxD girls. For example, in many fanfics, the male reader might gain special powers and use them to safeguard the girls from various threats in the DxD universe.
Another trope is the 'damsel in distress' where the reader gets into some sort of trouble and Damon has to come to the rescue. But sometimes this trope can be flipped, and the reader ends up saving Damon instead, which is an interesting twist.
One popular trope is the 'stranger to lovers' trope. In many 'Link x Reader Fanfic', the reader character starts as a stranger to Link, and through their shared adventures and experiences in Hyrule, they fall in love. It's a classic and always makes for an interesting read.
One popular trope is the 'adventure companion' where the reader character joins the Dragonborn on their quests. Another is the 'forbidden love' trope, perhaps between the reader and a certain character like a Thalmor agent in a world where such a relationship is frowned upon. And then there's the 'mysterious stranger' trope where the reader character arrives in Skyrim with a hidden past or special abilities that intrigue the other characters.
The 'rivalry - turned - love' trope is quite prevalent. At first, the futa and the reader might be rivals in some context, like in a competition or a battle of wits. But as they interact more, they start to fall in love. And then there's the 'redemption' trope. The futa character may have made mistakes in the past, and the reader is involved in their journey of redemption.
One popular trope is the 'enemies to lovers'. It could start with Abby and the reader having some sort of conflict or misunderstanding, and then gradually falling in love as they get to know each other better. Another is the 'hurt/comfort' trope, where the reader might be in a difficult situation and Abby comes to their rescue and offers comfort.
Some fanfics use the 'redemption' trope. Bowser might start off as his typical villainous self, but through his interactions with the reader, he begins to change for the better. There's also the 'mysterious stranger' trope where the reader is new to Bowser's world and he is intrigued by this unknown entity, leading to their relationship developing.
One popular trope is the 'Training Partner' where the reader becomes Goku's training partner. They start off as someone Goku helps to improve their fighting skills, and a relationship blossoms during the intense training sessions. Another is the 'Saved by Goku' trope, where the reader is in danger and Goku swoops in to save them, which then leads to a deeper connection. There's also the 'Power - up' trope where the reader somehow gains power with Goku's help and they go on adventures together.
One popular trope is the 'hurt/comfort' scenario. For example, Komaeda might be in a difficult situation, and the reader character comes to his aid, providing comfort. This trope allows for a lot of emotional depth and character development.