My sister, who has yet to reach orgasm with her boyfriend, buys a dildo through mail order and attempts to practice internal orgasms. The lewd sounds leaking from my sister's room... I sneak a peek, and the training scene is so erotic that I can't help but masturbate and get caught by my sister! Then, she approaches me, surprised at how similar her dildo is to my erect penis, and asks if she can try it out! My sister experiences internal orgasm for the first time with a real penis. Furthermore, 'It's okay to cum inside,' so I also experience my first internal ejaculation!!
