Betrayal is also a common theme. If someone they trust betrays them, Sonic and Tails would be deeply hurt and likely to cry. This shows their vulnerability. Also, the theme of feeling powerless. When faced with a force too strong for them to handle, like a powerful new enemy, they might cry in frustration and fear. It adds depth to their characters as they are not always the invincible heroes.
There might be a fanfiction where Sonic is injured severely during a fight with a powerful new enemy. Unable to move and in great pain, Sonic cries out of frustration and fear. This kind of story can explore his inner thoughts and how he copes with his own vulnerability. It could also lead to a story arc of his recovery and revenge against the enemy.
There's a fanfiction called 'Shattered Dreams' where Sonic is put in a situation that makes him break down and Tails has to be strong for both of them, but he also has his own moments of crying. It's really good at showing their friendship through tough times. Also, 'The Weeping Hedgehog and Fox' is a story that delves into their past traumas and how it surfaces in a moment of crisis, causing them to cry and lean on each other.
First, understand Sonic's character. He is a brave and confident hero, so for him to cry, there must be a really strong reason. It could be a situation that challenges his abilities and beliefs deeply. Second, describe the setting well. If it's a dark and desolate place where he's alone and facing a great threat, it can enhance the emotional impact. For example, if he's in a collapsing ancient temple with no way out and his friends are in danger.
A sonic crying fanfic may tell a story where Sonic is in a very difficult situation that makes him cry. For example, he could be trapped in a place from which he can't escape easily, and all his attempts have failed. This could lead to his frustration and ultimately his crying. Or it could be related to his past traumas resurfacing. The fanfic might then focus on how he overcomes these emotions or how his friends come to his rescue and help him deal with his feelings.
One possible plotline could be that Sonic fails to save Chris from a dangerous situation in time, causing Chris to break down crying. For example, if a powerful enemy captures Chris and Sonic has to fight through many obstacles to reach him. Another could be that Chris feels left out as Sonic spends more time with his other friends, leading to his crying and Sonic having to make it up to him. Maybe Sonic gets so caught up in his adventures that he forgets an important event for Chris, like his birthday.
First, you need to understand Sonic's character well. Know his strengths, weaknesses, and what could really break him down to the point of crying. Then, create a believable situation for his crying, like a personal failure or a threat to someone he loves. Also, use vivid descriptions to show his emotions, not just say he's crying but describe how the tears roll down his face and his body language.
Guilt is a possible emotional theme. For example, if Tails makes a mistake that he thinks endangers Sonic or the world, he would feel guilty and cry. Betrayal could be another theme. If someone he trusts turns against him, his crying would be a natural reaction. Also, the theme of inadequacy. If Tails feels he's not good enough to help Sonic in a crucial moment, that could bring him to tears.
In a fanfiction scenario, Tails might cry when he discovers that his past actions have had negative consequences on the Sonic X world. He's always been so eager to help, but if he realizes he accidentally caused harm, it could break his heart. Another situation could be that there's a natural disaster in the world they live in, and Tails is unable to save some of the small animals he loves so much, leading to his tears. And there could be a time when Tails is excluded from a group activity by mistake, and his feelings of being left out make him cry.
To best portray the emotional aspect, the author should focus on the build - up to Chris's crying. Maybe show the small disappointments or fears that Chris has been suppressing over time. When he finally breaks down, it will seem more natural. Also, the reactions of other characters around Chris, apart from Sonic, can add depth. If his family members are also sad or concerned, it can amplify the emotional impact of Chris's crying.