Over the years I have been caught masturbating in panties a few times.
My first was when my sister caught me in her room wanking In her panties. She was going to tell our folks, but refrained, on condition that I showed her everything. So I did.
She thought she was punishing me and humiliating me, I loved ever second. I stripped naked and showed her every detail of my rock hard penis, balls and asshole, wanking just inches from her face. I then wrapped her silky panties round my cock and pumped it hard, as she played with my precum that was leaking from my cock slit, and had me lick it from her finger.
I pulled her panties over my face and turned to wank for her, spreading my ass cheeks and fingering my bumhole. For my climax, I pulled on her panties once more and shot my load into her knickers as she watched my sperm soak through.
After that, we became partners in masturbation, she lent me clothes, did my hair and make up, and chatted with me about boys and sex. I guess we became more like sisters, which I treasure a lot.
Funnily enough, she was on the phone yesterday, and caught me in mid-wank, but that didn't stop me, and I really enjoyed chatting as I masturbated, finally spunking in my panties as we talked.