CAST

Sirius Black makes a bet with Lily Evans. If he can get a girl to fall in love with him in 20 days, Lily has to go on a date with James. If he loses he has to apologise to Severus, in front of the school.

At the same time...

Lyria makes a challenge with her friend. She can make a guy break up with her in less than 20 days.

What a coincidence that Lily picks her to be Sirius' girl.

This is based off the movie 'How to Lose a Guy in 10 Days' so the idea and plot belongs to the filmmakers.