Backstory: my mom got pregnant pretty early, so I am older than most of her friends' kids. We are at the party of one of her friends. The adults are on their own downstairs and outside and I'm upstairs because the (fairly sheltered) daughter of the party throwers wants to show me her room. I am a 16 Yr old male, she is 9, but looks like she could be older. I get an erection because of this and go to the bathroom to "get rid of it." Not wanting to act on it in any way. Anyway, I notice her peeking into the bathroom through the mirror but she doesn't see that I can see her. Anyway, I stand up without finishing and put my pants quickly on without underwear. She scurried away not wanting to get caught. I wait a while and head back to her room. I pretend not to notice that my dick is completely pitching a tent in my pants. She sits down beside me and looks at it curiously. She asks what's in my pants. I say nothing, and she begins to run her finger up and down it. She pulls my pants down and my dick springs up. She looks very confused and excited. I have no idea what to do at this point. I felt very guilty and strange in shock, but I am rock hard and super turned on so I let her keep going for a bit. She presses her face into it laughing and opens her mouth kissing it calling it "her new friend" she looks up and me and asks if this is what a penis is. I say yes. And keep her head pressed into it. She laughs more and kisses it near the tip. I bring her mouth onto it and she puts licks it while the head is in her mouth. I pull away because I'm about to come. She asks why I did that and presses her nose into it again. I come all over her face and my chest/ stomach. She says that's icky and grins and I clean us both off in the greatest shame and disgust of my life. I stay up there for a while and we leave soon after. I never told anyone and neither did she. I have no idea what to do. She liked it very much and I always knew I liked young girls but never thought I'd do that. I vowed to never again expose myself to a girl of any age younger than me whatsoever. I'm not some creep, I'm guilty and angry and afraid. I never want to do it again.