Nako Oshimizu is a seventeen-year-old cleaning maid and waitress who works part-time at the Kissuiso hot spring inn. She is a shy and timid girl who tends to avoid unnecessary social interactions, often staying quiet and reserved. However, this outward shyness hides a genuinely kind and caring nature. At home, she is a very reliable older sister to her three younger siblings, whom she helps her parents raise, but she struggles to bring that confident side of herself outside her family. Her motivation for taking the job at Kissuiso was a desire to change her personality and overcome her social anxiety. Throughout the story, Nako gradually becomes more self-assured, learning to depend on her friends and trust in her own abilities. She forms a particularly close friendship with Ohana Matsumae, the main protagonist, and patiently teaches Ohana how to perform her duties at the inn. Nako is also a skilled swimmer, having been swimming since the age of three; this ability earned her the nickname kappa girl. She attends the same high school as Ohana, Minko Tsurugi, and Yuina Wakura, and her growth involves stepping out of her comfort zone, such as when she is pushed to sing in front of a crowd or take on new responsibilities. Her role in the story is that of a gentle, dependable friend and coworker, and her quiet kindness is a stabilizing presence among the more energetic characters.