Older Sister Pinned And Tickle Tortured By Fat Friend

One of my friends from school who I'll call Danny is a good mate. Abit unpopular but he's cool and I had him over at my house last night. Thing is he has a crush on my older sister who is 8 years older than us. Shes always friendly and he takes what chance he has to talk to her. Anyway one time after having to visit the toilet I was coming back up and heard shrieking and laughing and when I peeked through Danny was on my older sisters legs tickling the hell out of her bare soles as he had ripped her socks off. She barely struggled to fight back and near the end he went up and got her belly Abit as well. After he finished she playfully slapped him and said that was just as mean as last time and he laughed and blushed
Last time?!
Should I be worried?