Source: https://kakuyomu.jp/works/16818093082402430116?
synopsis
In the Otome game, “Beyond the Sparkle, True Love,” the villainous stepbrother is always doomed to die in his sister’s doomed flag.
For some reason, I am reincarnated as such stepbrother──Yuran.
“Oh no, if this continues, I will die because of my sister’s doom flag. ……!”
Yuran desperately tried to learn the power to survive even if he was caught in the doomsday flag, and to prevent the flag from being raised, he stood by his sister, Tia, and helped her by presenting himself to her.
And as a result…
“Yu-kun, marry your sister!”
“Who!? Who said those things that tried to break the peace in the family?!”
…… She grew up to be a terrible brocon
She tried to bathe with me, she tried to sleep in the same bed with me, she tried to marry me.
How did this happen? However, I am sure that she has become more than just a villainess.
I’m sure of it, but…
“She made fun of Yu-kun! That’s unforgivable, no matter how much of a prince he is!”
“But that doesn’t mean you hit him!”
For some reason, Tia always brings a flag of doom that even involves her brother…