HUNBL-133 It's come to this... I'm sorry... The sister and brother being bullied at school are forced into incest

One day, my unremarkable sister unusually brought a school friend home… However, the friend was a girl who bullied my sister. When I went to my sister's room, she and her friend made me have sex for fun, causing me to lose my virginity forcibly! Then, I was made to have sex with other friends one after another… I became a sex toy. My sister's friend, getting carried away, said she wanted to watch my sister and me having sex… Although my sister and I resisted, we couldn't defy them and were forced into intercourse… In the end, we were even made to perform taboo internal ejaculation! Something went wrong with me…