One possible reason could be jealousy. Maybe Syrus is getting more attention in the fanfiction world, and Zane, being a proud character, doesn't like that. For example, if Syrus is praised for his skills while Zane feels overlooked, it can make him mad.
At first, their relationship might become strained. Zane's anger could make Syrus confused and a bit scared. Syrus might try to avoid Zane, not knowing how to deal with his anger.
Maybe Zane and Syrus get trapped in a strange virtual world created by some glitch in the digital system. They have to rely on each other's skills to find a way out. Zane's logical thinking and Syrus's knowledge of the digital realm might be combined to overcome the various obstacles like malfunctioning programs and security barriers.
It's quite normal. In a fandom, people are interested in different aspects of the characters. Zane might be curious about Syrus's backstory, relationships, or potential storylines that fanfiction writers have created. It's just another way of engaging with the fictional world they are part of.
Another aspect of their brotherly love in fanfiction could be the way they support each other during tough times. Syrus might be having a hard time with his self - confidence, and Zane would be there to encourage him. He could tell Syrus about his own insecurities when he was younger and how he overcame them, thus inspiring Syrus to grow and believe in himself more.
There's no way to really say if it's common without knowing more about Zane. If he has a lot of free time and is a die - hard fan of the source material involving Syrus, then it might be a regular pastime for him. However, if he's not that into the whole fan culture or Syrus specifically, it would be less common.
The main characters are clearly Zane and Syrus.
Perhaps Zane is a big fan of Syrus himself and by reading the fanfiction, he gets to delve deeper into the Syrus - centric stories. It could also be that he enjoys the creativity of the fanfiction community and how they expand on the Syrus character in ways the original work might not have.
He might be really bored or annoyed at first. Maybe he'll roll his eyes a lot and keep thinking about how he got into this situation.
The growth of their brotherly love can also be a theme. As Syrus matures, he starts to understand Zane better. He realizes that Zane's strictness was always out of love and a desire for him to become a better person. In turn, Zane sees Syrus growing into a confident individual, and this makes him proud and further strengthens their brotherly connection.
In the Yu - Gi - Oh fanfiction, when Zane gets stuck with Syrus, they might have an intense duel training session. Zane could be super strict with Syrus, pushing him to improve his dueling skills. Maybe Zane would share some of his top - secret dueling strategies that he's developed over the years.