You guys always assume that Suisei is the original personality, but I think it's the other way around, Anemachi is the original, not Suisei, the reason for this is because Suichan is everything that Anemachi wants to be.
Anemachi used to be an idol trainee with a pretty singing voice and appearance, furthermore, she is also bestowed by the gods with good personalities and a sense of morality in this depraved world. That poor girl just wanted to be an idol to bring joy and smile to everyone around her; however, that poor soul was soon exposed to the dark side of the idol industry.
To debut as an idol, Anemachi was called up to "serve" a CEO, of course, she refused and wanted to quit, traumatized by how disgusting her agency truly is. That fateful night, the last night she spent at the dorm with her other trainee friends was the night Anemachi got betrayed by her friends, she was forcefully tied by her "friends" wanting to debut and brought to the CEO.
The CEO did unspeakable things to her that night.
The experience completely shuts down Anemachi's mind, so to stay alive, her mind creates an alter ego, named Suisei Hoshimati, a sister that she can rely on and can talk to about her everything.
Suisei Hosimati is good at everything, she is the idol that Anemachi wanted to be. Suisei Hosimati doesn't have any breast, she doesn't have to ignore all the ogling Anemachi endured. Suisei Hosimati has friends that she can rely on, unlike Anemachi who was betrayed by her friends. Suisei Hosimati likes Shounen because Shounen is the transition between pure childhood into adulthood, a phase that the CEO stole from Anemachi, robbing her of her innocence in a flash.
Lastly, Suisei Hosimati is pure and has never had a boyfriend ever before, unlike Anemachi, who is now forever impure and stained.
