At the start of Sasameki Koto, 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 dojinshi 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 Munchausen (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, but Sumika is able to make up with her. 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.
This story has the part which was created by referencing Wikipedia, so the licence of GFDL is applied to this story.