Attacker You! is the story of ambitious and energetic thirteen year-old junior high schoolgirl You (pronounced Yoh) Hazuki, who moves to Tokyo from the Japanese countryside to live with her father Toshihiko, a cameraman recently returned from Peru, and attend school. You's mother is not in the picture, having left when You was very young. Also living with You and her father is her younger brother Sunny, who is very attached to his older sister and tends to follow her everywhere she goes, including to school and to her volleyball matches. However, You's father is not supportive of her volleyball playing, and You is puzzled as to why he gets so angry about it. You, who has exceptional jumping abilities, is passionate about volleyball and dreams of one day being a part of Japan's national women's volleyball team in the 1988 Seoul Olympics. She joins her school's girls' volleyball team and quickly becomes one of the top players, although Daimon, her coach, is brutal and behaves violently toward his players when they make mistakes or fail to live up to his expectations. You makes a loyal friend in the kindhearted Meiko (nicknamed "Chibi") and an instant enemy in the captain of the girls' volleyball team, Nami Hayase, a cold, arrogant girl whose entire life is volleyball and who doesn't take kindly to her bubbly new teammate. You and Nami also become rivals for the affections of Sho Takiki, the handsome, dashing captain of Hikawa's boys' volleyball team. You puts as much energy into trying to get Sho's attention as she does into her game, and even takes to attending extra training sessions coached by Sho in the morning before school just to be near him. Eventually, You and Nami form a tumultuous friendship, which comes to a head when Nami joins an opposing professional team coached by Daimon. You also befriends ace attacker Eri Takigawa, a girl from a rival team, the "Sunlight Players"; You and Eri eventually join the same professional team.
高身長の選手が犇めくコートの中を170cmという大きくない体で活躍する選手"小さな巨人"を見て以来、バレーボールの世界に魅せられた日向翔陽はたった一人でバレーボール部を設立。しかし、中学初にして最後の公式戦で"コート上の王様"影山飛雄率いる北川第一中学に惨敗してしまう。そして翌年の春、宮城県立烏野高等学校バレー部で2人はチームメイトという形で再会することになる。 その烏野は、かつて全国大会にも出場経験がある県下有数の強豪として知られていたが、彼らが入部した時は、主将曰く「強くも弱くもない中堅」のチームだった。だが、彼らは再びインターハイ制覇、そして全国制覇を目指して挑んでいくことになる。
東京の強豪中学に通っていた灰島公誓は、バレーチームで深刻なトラブルを起こしてしまう。その後、幼少期に過ごした母方の郷里である福井県に転移し、幼馴染だった黒羽祐仁と再会する。ずば抜けた身体能力でプレッシャーが弱くなっている黒羽と、バレーに圧倒的な情熱と才能があり摩擦を起こしたばかりだった灰島と共にエースコンビとして成長していくが、中学時代の最後の県大会で衝突してしまい、絶縁状態で2人は地元にある七符清陰高校に進学することになる。 七符清陰高校の男子バレー部では、熱血主将・小田伸一郎と、秀才で毒舌家でもある副主将・青木操の3年生コンビおよび日光アレルギーのため常に長袖長ズボンを履く棺野秋人を始めとする2年生たちが待っていた。新生バレー部はまもなく弱小チームの殻を破ることになり、福井県の新星として注目され成長していく魅力的なライバルが登場していく。