Brands by definition are stories embedded in the mind of the market. A good story has the ability to create emotion in the hearts of the listener, reader, or viewer.
The funny thing about stories is that although the arcs and endings change, a lot of the characters repeat themselves. These characters become our heros.
To understand your brand hero, start with yourself. Create a brand diamond of who you are with four different attributes.
Your company cannot be something you are not.
Once the character diamond is created for you (as founder), then apply those same attributes to your organization.
If you're having a hard time coming up with your character attributes, give me your top five favourite movies of all time. With that information, I can probably tell them to you. Our heros show up in things we enjoy (like movies, books, poetry, etc).
Once you identify your character attributes, you can tell the story from your hero's point of view (using similar arcs as your favourite movies).
You want a creative brand story to set your underwear apart, but literally the ONLY thing you have told us about your product is ... that it's underwear.
So any idea we may have would apply to ANY underwear. As a result, it's impossible to help you set your brand apart.
What makes your product unique? What are you doing that the competition isn't? Whom are you trying to reach?
I'd definitely need to know who and what and why you are, to hear your story in your own words from you, before I could translate those characteristics and goals into a brand story that appeals to your target audience. You tell us, then we tell others.