Sweet Breaker's real name is Amami.[1] She also doesn't mind being called that name.[2] You can also get her real name in game by repeating selecting Sweet Breaker in Character Roster.[3]
The release of Sweet Breaker as a playable character in 100% Orange Juice! was teased in an April Fools announcement shortly before she was added.
Sweet Destroyer and 
Melting Memories. She also appears in the artwork for 
Sealed Memories.