Build their backstories in a way that they can connect. If your OC has a tragic past related to losing their family, Sansa can relate to that as she has also lost many of her loved ones. Have them share these stories slowly over time. Don't rush into the romantic part. Let them be friends first, support each other in difficult times, and then the romantic feelings can develop more naturally. For instance, the OC could help Sansa when she is dealing with the political pressures in Winterfell, and in return, Sansa could introduce the OC to the important people in the North to help the OC achieve their own goals.
Give them common goals. In the Danganronpa world, survival and solving mysteries are key. If the OC and Kirigiri both have a strong drive to figure out what's going on in the school, they will be forced to work together. As they overcome obstacles in their investigations, their relationship will naturally grow. For instance, they might have to rely on each other's unique skills to get out of a dangerous situation. Also, show their flaws and how they accept each other's imperfections. Maybe the OC is a bit impulsive at times and Kirigiri is overly cautious, but they learn to balance each other out.
By showing their shared interests. For example, if both are into building things or exploring, it gives a natural reason for them to bond. Just like how Phineas loves his big - scale projects, if the OC also has a passion for creating something amazing, they'll easily click.
Develop their backstories well. For example, if the OC has a tragic past, show how Simba's own experiences can help him understand the OC. This shared understanding can form the basis of their relationship.
You should also develop their individual personalities well. If Gray is his usual cool and sometimes aloof self, the OC could be someone who is warm and outgoing, which initially clashes but then becomes an attraction. Have them learn from each other. For example, the OC could teach Gray how to be more open about his emotions, while Gray could teach the OC how to better control her magic in combat situations. This mutual growth will make their relationship seem more real.
Give them common goals. For example, if they are both trying to save a certain group of people or protect a particular place. Working towards the same objective will naturally bring them closer and make their relationship development seem more real. Also, show their flaws and how they accept each other's imperfections.
For making their relationship believable, you should show the development gradually. For example, if it's a friendship, start with small interactions like sharing a meal or a common interest. If it's a romantic relationship, let them first get to know each other's personalities. The OC should respect Android 21's nature, whether it's her fighting side or her more gentle, food - loving side. Also, have them face challenges together that strengthen their bond.
Writers can make it believable by giving the OC a strong backstory. For example, if the OC has a past that somehow ties in with Tom's, like they both come from similar difficult family situations. This can create an instant connection. Also, showing their gradual development of feelings rather than instant love is important.
In a fanfiction, details matter. Describe their body language when they are around each other. For instance, Simon might blush when Jeanette smiles at him, or Jeanette might play with her hair when she's talking to Simon. Also, include their internal thoughts about each other. These little things will build up a believable relationship that can lead to a moment of making love. For example, if Simon has been thinking about how much he cares for Jeanette for weeks and Jeanette has the same feelings, it will make their love - making scene more believable.
One way to make their relationship seem more real is to add some obstacles. For example, there could be another person who has a crush on either Bella or Mike. This creates some tension and jealousy. Also, describe their physical and emotional attraction in a more nuanced way. Don't just jump straight into the'make love' part. Let their relationship build over time, with hugs, holding hands, and long talks before any more intimate moments.
To make their relationship more believable, show their gradual development of feelings. For example, start with small gestures like Sully bringing Michaela flowers from the forest or Michaela making Sully a special meal. Then, as they interact more, they start sharing their dreams and fears. This build - up makes it more believable when they finally make love as their relationship has been growing steadily.