One main element could be loneliness. Since Jigglypuff is often depicted as a cute and friendly Pokémon, it would be really sad if it was left alone. Maybe all its friends left for some reason, and it was left behind, feeling abandoned.
Well, one possible sad story of Jigglypuff could be that it always tries to sing lullabies to put others to sleep but often gets ignored. It puts so much effort into its sweet singing, yet people or Pokémon just walk away or don't appreciate it. It's like an artist whose work is not recognized.
The main sad elements in the Frankenstein story are numerous. Firstly, the Creature's birth into a world that instantly despises it. It has no choice in how it looks or is made, yet it is punished for it. Secondly, Frankenstein's own inner turmoil. He loses his family and friends because of his creation, and he is filled with guilt. And finally, the cycle of pain. The Creature's pain leads to revenge, which causes more pain for Frankenstein, and this cycle just goes on and on, creating a very sad and tragic narrative.
Imagine Kirby bouncing around in a meadow and suddenly hears Jigglypuff's song. Kirby has never heard such a lovely sound before. He approaches Jigglypuff, and Jigglypuff stops singing for a moment, a bit startled. But Kirby's big, innocent eyes make Jigglypuff relax. They start to interact. Kirby shows Jigglypuff his amazing ability to inhale enemies, and Jigglypuff shows Kirby how it can inflate itself. As time passes, they develop feelings for each other. Their love story is like a fairytale in the world of cute characters, full of discovery, friendship, and eventually, love.
In such fanfiction, Kirby is often depicted as his cute, round self, but with a more tender side when it comes to his feelings for Jigglypuff. He might use his unique abilities to protect or impress Jigglypuff.
One main element could be loss. Maybe Sonic loses a power - up or a special ability that he has relied on. This would put him at a disadvantage and make him sad as he tries to adapt.
Betrayal is a main element. Judas' betrayal set in motion the events leading to Jesus' death. Another is the unjust trial. He was falsely accused and condemned. And of course, the crucifixion itself is a key part. The pain and humiliation he endured on the cross was extreme.
The main elements include her family issues. Her relationship with her sister is strained. And also the environment she grew up in. A violent and unstable place that didn't give her a chance to grow up healthy. Plus, her own inner turmoil that drives her to do bad things.
One key element is the princess herself. She is often in a powerless position despite her royalty. Another is the source of her sadness. It might be due to external forces such as political arrangements, like an unwanted marriage for the sake of an alliance. Or it could be internal, like her own unfulfilled desires. Also, the setting of the story, whether it's a gloomy castle or a foreign land she's forced to go to, plays a role in emphasizing her sadness.
Perhaps loneliness is a main element. If Reigen was often alone in his journey, it would be sad.
The death of Paul Gray is a main element. It left a void in the band. Without him, their music and live performances had to be re - imagined.