It took place within a star dome they were making. There was a group of 5 (3 guys 2 girls) the first couple went in to check if it was dark enough and they slowly by surely had sex while the mc and the main girl was there outside and heard everything. After the couple left the cook guy of the group ask the girl to see if they both could check it out and ask mc to watch out of the teacher. As they went in cool guy ask if she wants to have sex and they did. This is basically all that the doujin had.