Flowers of Evil

Flowers of Evil (악의 꽃) is a seven volume manhwa created by Lee Hyeon-Sook in which siblings Se-Joon and Se-Wa are a bit too... close to each other.

Se-Joon and Se-Wa are siblings with a dark, complex relationship. Se-Wa, a girl considered psychotic by others, is attached to her brother... a little too attached. In her eyes, there is only Se-Joon, and no one else. And what of Se-Joon's feelings?

This manhwa features examples of:

 * All Love Is Unrequited: Se-Jun says loves his sister as a sibling, though sometimes his behaviour hints at feelings which mirror hers.
 * Alpha Bitch: Whats-her-name claims that she saw Seh-Wah  with her own eyes.
 * Big Brother Attraction: Se-Wa as a teenager.
 * Bishonen
 * Brother Sister Incest
 * Clingy Jealous Girl: See 'Yandere'.
 * Disproportionate Retribution: See 'Yandere' as well. Poor afro-perv-guy...
 * Downer Ending
 * Everythings Better With Princesses: Se-Wa's nick-name around school is 'The Ice Princess'.
 * Father I Want to Marry My Brother: Se-Wa as a child.
 * Green Eyed Monster: Jealousy and envy are the roots of all 'yandere' in this story.
 * Incest Subtext: Se-Wa is both vocal and forward about her feelings for Se-Wah. His feelings about her are conveyed more subtly.
 * Love Triangle: Actually, more of a square.
 * No Export for You
 * Played for Drama: The premise is about two twins who want to jump one another's bones. Just another run-of-the-mill romantic comedy where it turns out they're not siblings after all, right?
 * The Reveal:
 * She Is All Grown Up: We are treated to a few shots of the twins when they were younger. Thing is, now that they're older a lot of the things they used to do together are not okay anymore. Like, sleeping together. Or bathing. Or kissing.
 * Sins of Our Fathers
 * Unlucky Childhood Friend: How Se-Wa sees herself with regards to Seh-Jun.
 * Unresolved Sexual Tension: Seh-Joon and Seh-wah.
 * Wounded Gazelle Gambit: See 'Yandere' again.
 * Yandere: Seh-Wah, and
 * You're Insane: Seh-Wah gets this a few times,
 * You're Insane: Seh-Wah gets this a few times,