Mary has a pretty severe fear of fire. She's gotten better at dealing with it over time, but for a long time being near any kind of open flame could cause her to have a panic attack

Already answered (https://retrospring.net/@Zeroes_King/q/108945870946892501)

Mariah is terrified of being helpless/powerless in a dangerous situation where others may be in danger, so that is part of what drives her to get stronger. She’s also haunted by the reality that she can’t save everyone from pain.

Andre is afraid of being all alone, but he’s also scared of letting people get too close to him for fear of being hurt.

Already answered, but short answer: Pikachu

Casey is afraid of being forgotten really, but he is also afraid of Ghosts