Drifting Home (2022) on Netflix

Plot summary

At eleven, Kosuke Kumagaya and Natsume Tonai have grown up like siblings at the Kamonomiya housing complex, where Natsume also lived with Kosuke's grandfather Yasuji. Their friendship has been strained since Yasuji died. One summer day Kosuke and his classmates from Kamo Elementary School, Taishi, Yuzuru, Reina and Juri, slip into the complex, which is set for demolition and known by the children as the ghost housing complex. Kosuke runs into Natsume there, and she tells them about a mysterious boy named Noppo who lives in the building. Kosuke and Natsume argue, the others join in, and heavy rain falls. When it stops, the complex is adrift on an ocean with only the children aboard, and they explore the floating buildings nearby in search of food.