Natsuiro Kiseki Season 1 Episode 9

Saki on the Tip of the Sky of the Journey

Upon arriving at their accomodation, the girls meet Chiharu Okiyama, the twin sister of the lifeguard from earlier, Koharu. Whilst trying to hide Saki from the neighbours in the hot springs, they inadvertently discover a wishing rock in the hotspring that causes Saki to turn invisible, unable to be seen or heard by the others. Later that night, as Natsumi talks with Yuka and Rinko about her desire to stop Saki from moving, they remind her that they'll still be friends regardless. The next day, the girls join Chiharu around the town. As they explore the hospital Saki's father will work at, Koharu becomes hostile towards them as he didn't want the doctor who used to work there to be replaced, but Chiharu assures her that she isn't the only one who misses him. As Saki comes to accept that she'll be moving here, she becomes visible again.