I'm looking for a hentai oneshot featuring an older brother and his sister (both looked like teenagers). I came across it a while ago and can't remember it. If my memory serves me right, the older brother coerced his sister into having sex and they do it in the bathroom. The sister was worried their mother can hear them so the brother muffled her mouth with his hand (or something like that). I remember the art being pretty nice and clean.
Thank you in advance!

I'm pretty sure it's Closing Sister.
The scene you are describing happens right before the oneshot ends.

Remembrance, a forsaken thing that revokes ignorance and leaves people in doubt, is my only redemption and solace deep within the cascade of white.

The evergreen trees speak of days long past when music mingled with the wind and sweet murmurs brushed our cheeks.

Yes, that's it. Thank you so much!