My stepsister, who never takes off her mask outside her room, shyly removes it! HUNTB-638

My parents' remarriage gave me a new stepsister who wears a mask every time she eats, except when she's in her room. Now the mask has become an extension of her face. But as her brother, although we're finally family, I can't properly see my sister's face! So I tried to persuade her not to wear a mask... but she told me that if I wanted to take it off... that left me speechless with shock. However, because I also wanted to see her breasts, I accepted this compromise, and of course, I got an erection! And then...