She became actually abusive, at first it was rather tender and affectionate as far as I remember, she'd touch me but not really go further than that. We'd just lay together naked and she'd cuddle me super tight. In time she started doing more and more things, she'd force herself on me, and especially by the end became violent and would hit me where my parents wouldn't see it through my clothes. She eventually started shoving things into my ass which would tear it, and other shit. Around 11 or 12 she did start actually fucking me too, and twisted me all up inside with what she'd tell me about being such a shitty kid than I needed punishment, that I was only hers and more. She'd choke me out by sitting on my face or get me erect then twist my dick and hurt me.
Not all sexual relationships between kids and older adults is like that but even if they're not physically damaging they're mentally and emotionally damaging. For over a decade I still felt as if I deserved all that and sought out destructive and abusive relationships as a result. It really destroyed my self confidence, it damaged me physically, but the emotional and mental scars run far deeper.