Perhaps in this fanfiction, Zane gets mad because someone cheats in a Yu - Gi - Oh tournament. He is a very competitive person and values fair play, so when he discovers the cheating, his anger flares up. He might then take it upon himself to expose the cheater and uphold the integrity of the game.
Maybe Zane gets mad when he loses an important Duel in the Yu - Gi - Oh world. It could be that he was so confident in his strategy but his opponent outsmarted him, leading to his anger.
It could be his rival. Rivals in Yu - Gi - Oh are always trying to one - up each other. If his rival manages to steal a rare card that Zane has been eyeing, or if the rival taunts Zane about a recent defeat, that would surely make Zane mad.
Maybe Zane gets mad because someone stole his special item. It could be a magical sword or a unique piece of technology in the fanfiction world.
Well, maybe Atticus stole Zane's special item. That would surely make Zane mad.
Atticus and Zane could be characters created by the fanfiction writer. They might be friends, rivals, or even siblings in the story's universe.
There could be a rival character, let's say Jack. Jack might be constantly provoking Zane, which eventually makes Zane mad.
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.
Well, perhaps in the fanfiction, someone could have insulted Kuroko's basketball skills. Kuroko, usually so calm and reserved, gets mad and decides to show off his real capabilities on the court in a very intense and uncharacteristic way. He might start trash - talking his opponents, which is something he never does normally.
In a 'yami gets mad fanfiction', it could be that Yami discovers a betrayal. Suppose he trusted someone deeply in a magical world they inhabit together, and that person has been secretly working against him. This realization makes him extremely mad, and he has to decide how to deal with this traitor while also protecting his friends.
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 in the fanfiction, Atticus and Zane are friends, and Atticus is just being a good friend by suggesting Zane to shave. Zane could be going through a rough time and has let his appearance go. Atticus, seeing this, tries to get him to shave as a way of getting him to take better care of himself and regain his confidence.