Sins.

Soulmates exist now.
In a world where Sinning is acceptable, if not encouraged, Soulmates are discovered through tattoos. When you Sin, a tattoo appears on your Soulmate's skin. Once two Soulmates enter a five foot radius of one another, the Sins will glow, indicating you've found your partner. After that, it's all history.
Today is Lusia's birthday, still no tattoo on her body. She's given up on her Soulmate, all she has is herself.
Told through the perspective of six characters, Lusia fights to protect herself from a cruel world, unaccepting of her tattooless body.