Yukako Yamagishi Falls in Love, Part 3 (山岸由花子は恋をする その③ Yamagishi Yukako wa Koi o Suru Sono 3), originally The Great Badmouthing Strategy!! (カゲ口大作戦!! Kage Guchi Dai Sakusen!!) in the WSJ release, is the thirty-first chapter of Diamond is Unbreakable and the two hundred ninety-sixth chapter of the JoJo's Bizarre Adventure manga.
Koichi, Josuke and Okuyasu meet near the swimming pool. Koichi is confused as to what he has to do with Yukako, saying that it still pleased him a little when she confessed to him. Okuyasu feels him, feels him deeply and his feelings he can feel deeply. Koichi decides to bluntly tell her off, but Josuke objects at the idea, arguing that it will have the reverse effect and only make her more determined. In order not to antagonize Yukako, Josuke proposes to ruin his image, so that she lets him by her own accord. Between choosing either looking like a momma's boy or a filthy boy without hygiene, he picks the second choice. Josuke and Okuyasu then get overboard with their ideas, proposing that Koichi shoplifts or pretends to be gay, which Koichi refuses as with his current grades, he risks ruining his life. Nonetheless the three promise to try to and disgust Yukako away from Koichi.
Later Josuke and Okuyasu openly slander Koichi as Yukako passes, who stays emotionless but listens to them anyway. They talk about how Koichi really steals, him cheating during the exams and how he doesn't have any future.
That night, Koichi has trouble sleeping and is anxious about Yukako. When he finally falls asleeps, he then has a nightmare of her coming toward him. He suddenly wakes up and see Yukako at his window, and tying him with her Love Deluxe, Yukako enters Koichi's room, telling him that she's decided to make him a better man. Seeing Koichi's 16 out of 100 in English, Yukako then kidnaps a powerless Koichi who understands that Josuke has made things worse.