Sister Got Naked

this happened when I was 15.my sister was 14.our parents were out for the night.we decided to go the cinema to see the Karate kid....
She came in my bedroom said she couldn't go because she had a problem. .i said not to worry.she insisted on showing me.she took down her pants, & showed me she had hair & there was a bit of blood.i said not to worry.she was just becoming a woman..she spread her legs for me .it was the first time I'd seen a real vagina.i put a finger in her., touched her breast..and we've never spoke of it again.