Well, she was 10 at the time, and we were in my granduncles house near the beach.
I had gone there with my parents and my brother. My cousins lived around the corner and used to come by to play with us.
Well, one day my parents left with my brother to go to the beach while I stayed at home. My granduncle was left in charge, but it was 16:00 and he went off to take a nap; I've never been a fan of those so I just fucked around the house for a bit before my cousin came. She was surprised no one was there and she introduced me to a game she called "playing Indians". She asked me to tie her up to a bed, and that's what I did. No idea what she intended at the moment.
Then she told me to do naughty things to her body while she was strapped to the bed. She said she wanted kisses, caresses and tickling.
Me, being a little 8 year old beta, chickened out, untied her and hid in my room out of embarrassment.
We never discussed it again and we pretended it never happened.