Send ♕ for a CHILDHOOD headcanon.
As a child B-ko was often transferring from school without her parents considering the effects on their own daughter. Due to switching schools as frequently as she did B-ko was often isolated, treated as if she were some creature by the other students. They never accepted her. Seeing as she never fit in, of course other students often used her as a target of mistreatment. The other children were quite cruel, never so little as giving B-ko the chance to make friends. When she moved schools again the cycle only repeated, until she realized by creating an ideal girl or becoming someone she wasn't perhaps she would have less enemies and more allies.
Send ␛ for an ANGER headcanon.
Anyone who know's B-ko as the perfect girl who was good in every aspect could never imagine the anger she is constantly concealing. Only a select few are aware of the real B-ko who happens to be ragging with emotions every moment. Only when her mask is broken are these feelings exposed. One may see her as the perfect girl, a modest girl who could never hurt a fly could never imagine the anger B-ko is often keeping hidden under a kind face. Reality is she is one to loose her temper with others due to their poorly thought actions, she could even call them morons. Just knowing not a single person would ever know these ragging emotions inside irritated her. Of course they wouldn't know that. After all no one knew the real B-ko anyways.
Send ♆ for a BODY headcanon.
When B-ko was younger her appearance meant little to her, however following certain incidence and after realizing to be accepted she must change who she was B-ko began changing how she looked at that. To become the perfect B-ko she had to have an appealing appearance as well, right? Little things like taking care of her hair, styling it, staying active, dressing a certain way etc. By presenting in a way that made other students view her as the ideal girl in both appearance and personality she was now accepted by her peers.
Send ϡ for a MENTAL STATE headcanon.
Though she seems like a very capable and confident girl, true be told she is very unstable. Simply knowing there isn't a single person who will ever know the real her has a huge impact on this. It is as if she has two personalities, the way she wants to be seen and how she really is. Trying to keep this two personalities in order causes outbursts of emotion where she can't control them. She takes out her aggression on certain people or objects using violence. If one day more people were to discover this dual nature of hers she would undoubtedly snap.
Send ☂ for a FOOD headcanon.
Of course as the perfect girl she could never be seen stuffing her face like some kind of animal, right? B-ko eats small portions, and chooses healthy foods over baked goods or any thing that may affect how she is seen by others. Whether her diet was of healthy portions or not wasn't something B-ko really cared about, as long as whatever she was eating kept the perfect mask she had created in tact.