Rei was a transmigrator who was supposed to be a villainess that bullied the heroine. But somehow, the gender was wrong. Rei in the game was a woman but the transmigrator Rei was a man. He befriended Yuki, one of a hidden character who had a rare dark attribute. Yuki was also a transmigrator and like Rei, she came with a wrong gender. Yuki was supposed to be a man but she became a woman instead. And then Rei started to fall in love with Yuki and they got engaged after the courtship.

Because he was a man and he loved Yuki, Rei didn't care about the heroine at all but because he didn't bully the heroine like in the original game, the capture targets didn't adore the heroine as much as it should be. The heroine decided to frame Rei but it was backfired to the heroine instead. Rei also used that occasion to announce his real gender and his engagement with Yuki.

What made me puzzled was:

Yuki's fiancé is a woman in the body of a man crossdressing as a woman because of some childhood illness (if I understood correctly, Rei had a shock when she found herself in a male body and the doctors recommended dressing as a woman to counter the body dysphoria? Maybe? The text glosses over the details).

Rei - the fiancé - expected that she'd be attracted to men when she first transmigrated, regardless of her new physical s*x but finds out she likes women now and falls in love with a gender-bent secret character (Yuki, the female MC, who was supposed to be a man).

Rei uses everything she learnt from her former boyfriend to woo Yuki, her current girlfriend.

I would really have loved to read a longer story with this premise and these plot twists!!

Unfortunately, the story's so short that the characters feel shallow and unmemorable.