Summary: From what I understand from translating the descriptions, the characters Yukika Takamine and Haruto Aiba are estranged childhood friends who still have feelings for each-other. The work is mostly from the POV of Haruto who is getting off imagining(?) her banging random dudes for some reason, despite how she clearly still has a crush on him to the point of getting aroused. But I guess that's the style for this particular work, though the number countdown implies they may eventually actually reveal their feelings.
Please support the artist if you enjoy their work! https://www.dlsite.com/maniax/work/=/product_id/RJ362913.html https://f7xl5wl6a.fanbox.cc/posts/3135833 https://www.pixiv.net/en/artworks/94790610 https://twitter.com/alaruck_tui089/status/1464920586316959745