I'm not sure what the sister was expecting when she told them to 'keep things decent'. Did she secretly want them to disregard her words completely and go all the way? Should've been more specific in the first place.
Thanks for the TL. Pretty sure that second to last panel on the final page should be "he was waiting for my reply", not the other way around, since the read notification popped up as soon as she sent the sticker.
This kinda manga tends to do that only when it's not an adaptation. LN series very often get the relationship started in the first few volumes before going SoL with the couple.
I'm not sure what the sister was expecting when she told them to 'keep things decent'. Did she secretly want them to disregard her words completely and go all the way? Should've been more specific in the first place.