Left Alone(レフト・アローン,Refuto Arōn) is the 11th episode of Kids on the Slope anime. It was first aired on June 21, 2012.
Early the next morning, Kaoru keeps Sentarō from abandoning his house for good. When Sentarō's foster father reunites with the family, Sentarō feels satisfied when receiving from him an expensive fountain pen, confirming that he treats Sentarō as his own son. Kaoru and Sentarō ask Tsutomu to perform with them for the upcoming school festival, and they later convince Ritsuko to be the vocalist of the group. At the night before the festival, Sentarō, realizing Kaoru forgot some sheet music, he sets off to deliver it to Kaoru by scooter. The next day before the festival, Ritsuko tells Kaoru that Sentarō got into a car accident the night before, prompting Kaoru to rush over to the hospital. Sentarō is said to be fine, but his younger sister Sachiko, who was riding with him, suffered a head trauma and is in critical condition. Kaoru comforts Sentarō on the roof of the hospital, but he wakes to find that Sachiko has awoken and Sentarō has run away. Kaoru tries to comfort Ritsuko, but realizes that Sentarō will never come back.