Whispered Words (Japanese: ささめきこと, Hepburn: Sasameki Koto) is a Japanese yuri manga series written and illustrated by Takashi Ikeda. It was serialized in Media Factory's seinen manga magazine Monthly Comic Alive between March 2007 and November 2011, and was compiled into nine tankōbon volumes. A canon Drama CD musical spin-off was released on 23 Dec 2009, titled The Longest Day of Sumika. The series has been licensed in North America by One Peace Books. It was adapted as a 13-episode anime television series produced by AIC that aired between October and December 2009 on TV Tokyo. The series, which is set in a co-ed high school, is about Sumika Murasame, a 15-year-old girl who is secretly in love with her female best friend, Ushio Kazama. Ushio likes girls too, but is only into "cute" and "small" girls, while Sumika is tall, good at sports, and outgoing rather than shy.

Sumika Murasame is a high school girl who is in love with her female best friend Ushio Kazama, but is unable to confess how she feels as Ushio only likes girls she considers to be "cute" and "small", while Sumika is tall and athletic. Sumika discovers one of her classmates, a boy named Masaki Akemiya who likes her, started cross-dressing to catch her attention, but inadvertently was hired as a model. Sumika and Ushio get to know two girls in their class who are a couple, Tomoe Hachikusa and Miyako Taema; Tomoe wants to start a "girl's club" where only lesbians can join but is wrought with opposition. Sumika agrees to go on one date with Masaki, who comes cross-dressed as his female persona Akemi Yamasaki. Sumika becomes involved with her classmate Azusa Aoi, a quiet girl and aspiring writer who plans to attend a dōjinshi convention fueled by her love of yuri author Orino Masaka, which is the pen name of Ushio's older brother Norio. Sumika gets roped into helping Azusa and attending the summer convention as well, despite wanting to spend time with Ushio.

After the sports day competition and cultural festival, a short German high school girl named Charlotte Münchhausen (nicknamed Lotte), comes to stay at Sumika's home and dojo to train in karate. Sumika, who had quit karate because it is not "cute", starts training again to help in Charlotte's training, much to the joy of Sumika's father. Ushio is unhappy about Charlotte's training and merely wants her to be a gentle, cute girl. Charlotte gets sick after running in the rain during training, and after Ushio confronts her about it, Sumika lashes out, distraught how she cannot become any cuter or smaller. Following Tomoe's suggestion, a female karate club is formed with Sumika as the president and Charlotte as the vice-president. After Ushio starts realizing she has romantic feelings for Sumika, she starts to worry that Sumika may stop being friends with her. Masaki stops being a fashion model after being traumatically exposed as a cross-dresser.

After Sumika and her friends enter their second year of high school, two first-year girls named Mayu Semimaru and Koino Matsubara join the female karate club. Sumika is troubled over her relationship with Ushio, which has an adverse effect on her karate performance, much to the disappointment of Mayu. Sumika starts to get more involved with karate training to take her mind off of Ushio and in doing so, inadvertently distances herself from her. Ushio breaks down in depression because of this distancing, which results in Ushio breaking her arm, but is able to make up with Sumika. Tomoe accidentally implies to Ushio that Sumika has romantic feelings for her, much to Ushio's surprise, and Ushio finally accepts that she has fallen in love with Sumika but decides to become less dependent on her friend before confessing because she believes love will always fail for her. Meanwhile, Mayu realizes that she might have romantic feelings for Sumika as well, which distracts her in a karate tournament. Later, Sumika runs for student council president, though runs into various problems concerning rumours about her, and is forced to recede when Mayu ends up punching another student for insulting Sumika. As such, Ushio ends up becoming the new student council president.

Whispered Words was written and illustrated by Takashi Ikeda. After joining an independent film crew while in college, Ikeda decided to start drawing on manga as a way to create projects all on his own. His second manga work was submitted to the Shogakukan magazine Big Comic Spirits and subsequently won a small award. Whispered Words was originally conceived as a one-shot manga by Ikeda. Media Factory featured it in this for in the March 2007 of its magazine Monthly Comic Alive before picking it up for full serialization a few months later. After Whispered Words was translated for North American release, Ikeda stated he was unsure if would ever create another yuri-themed manga. Ikeda later authored the yuri manga series The Two of Them Are Pretty Much Like This, which was serialized on publisher Gentosha's Comic Boost website between January 2020 and February 2022 and localized in North America by Seven Seas Entertainment.

The Whispered Words manga was serialized in Japan in Media Factory's seinen magazine Monthly Comic Alive between its March 2007 and November 2011 issues. The chapters were collected into nine tankōbon volumes released between December 22, 2007, and January 23, 2012. One Peace Books localized the manga for North American release, compiling the original nine tankōbon volumes into three larger graphic novels and releasing the series between May 13, 2014, and March 17, 2015. The manga has also been licensed for release in Taiwan by Sharp Point Press.

A Drama CD musical was released on 23 December 2009 titled The Longest Day of Sumika. The events of the CD are canon and referenced in the manga, taking place during Sumika's birthday in the first year of the story.

A 13-episode anime television series produced by AIC aired on TV Tokyo and TV Aichi between October 7 and December 30, 2009, with rebroadcasts on other stations and AT-X a few days later, and was simulcast by Crunchyroll. The anime takes plot material based on the manga, with the exception of episode twelve, which is an anime-original story. The opening theme song is "Kanashii Hodo Aoku" (悲しいほど青く, So Blue it is Sad) and the ending theme song is "Niji-iro Pocket" (虹色ポケット, Rainbow-colored Pocket); both songs are sung by Natsumi Kiyoura.