Sometimes, heroes or heroines, had a sad or dark past which they don't talk about until a villain or they reveal their secret to their friends.
Here's why they keep it a secret:
- Terrible childhood like get bullied, unwanted, unloved, betrayed by their love one and saw their death of their parents or friends by villains, sickness or central death.
- Afraid that their friends will hate them who they really are.
- Afraid to lose the people they loved if they told them about their past.
- Used to be loved by someone until one day, everything they care of (lost family/friends, lost fame, saw the death of their family/friends, betrayed by their friends, had a ex-girlfriend/boyfriend leave them with someone else, etc.) make them to hate or don't trust everyone until a hero and/or heroines of the story show them what they're missing in their life like love, family, working together and/or friendship.
Opposite of Villains who had a secret past