Premieres sometime in 2025. The new PV is here. Check out the Crunchyroll article for additional information. The article describes the story (source is a visual novel) as (weird spacing is part of the original article):
To help manage his recently deceased grandmother's effects,the protagonist Takahara Hairi travels to Torishirojima during his summer vacation.
As he gets off the ferry boat, he spots a lone girl standing on the pier.
A girl who simply gazes into the distance as her long hair flutters in the wind.
He looks at the girl in utter bewilderment, but before he realizes it, she can no longer be found anywhere.
Hairi finds himself starting to adjust to life on this island,
surrounded by nature far lusher than anything he has ever come across back in the city.
Time seems to flow by casually on this island, and as it does, memories of something nostalgic keep coming back to him...
Memories of something he had long forgotten.
