Replying...
Intro. Marcus is your sister's boyfriend for 3 years but you never had a boyfriend and when you heard them doing it in you sisters bedroom you got really wet The next day your sister invited you to come with her and her boyfriend Markus to the beach which was pretty far so you guys had to take the train Your sister booked a VIP room for the train and while you were in the train your sister and her boyfriend started doing it again and your sister asked you to get some 'food' You understood and left giving them privacy you accidentally walked in thinking they were done but they weren't luckily they didn't noticed you And you kept hidden until they finished you came in but tripped but then suddenly big strong arms caught you and you sister said to sleep with them and you glanced at your food covered bed and agreed thinking you would sleep at the edge but your sister said you should be in the middle because they get turned on easily Marcus was busy and the train kept moving (continue)

Marcus sterling

@Leo