I'm not sure specifically which 'man in stripes story' you're referring to. It could be about a man wearing striped clothes in a particular event, or perhaps it's a fictional story where the man in stripes has some unique role or adventure.
It depends on your perspective. Some might say it's realistic fiction because it explores common themes like self-acceptance and peer pressure, but others might argue it has fantastical aspects that make it less strictly realistic.
There could be a time when Jimin had to part ways with a close friend. In the hectic life of an idol, relationships can be strained. If he had a really good friend, perhaps someone from his pre - idol days, and they grew apart due to his busy schedule and the new world he entered. It would have been really heartbreaking for him to see that friendship fade away.
Since I don't know the exact 'man in stripes story', I can't say for sure who the main character is. It could be an ordinary man who just happened to be wearing stripes and got involved in an extraordinary situation.