There is no foreseeable scenario in which this ends well for Sayaka.
Yuu already stole those lips, and already confessed her love. Sayaka's shooting for second place in every aspect without even realizing.
Sayaka is going to get the heartbreak she always had coming. Yuu has had too much development and focus for her arc to come up empty.
Win or lose, Yuu already took all the important firsts.
Just a little reminder than the delinquent is a rapist: 'The more they resist the more turned on I get...'
Yeah right she fell in love and she might act cute because of that, but that doesn't clean the shit out of her face.
Those who repent and reform should be offered forgiveness.
A momentary misdeed does not make a sinner for life.
To refuse the repentant the chance to be redeemed, you display a wicked cruelty of your own.
Hair dye is typically against school dress codes. Delinquency means minor crime. So silly little violations like that make them delinquents, despite having an otherwise agreeable attitude. Rules are rules.