Natural Vacation The Animation / Unforgettable Holidays!

The hentai is based on a visual novel of the same name by the studio Hibiki works. The art and character design was done by Asami Asami. 

Kairi-kun just got off an air-conditioned bus. He had to squint from the blazing sunlight to see anything at all. However, once Kairi's eyes adapted, an incredibly beautiful view opened up before him - a sparkling azure ocean, white fluffy clouds, a gentle salty breeze. He moved from Tokyo to this provincial village to his grandfather's place, after his parents went abroad. The kind and caring villagers warmly welcomed the boy, including two beautiful young girls, Haruka and Yuzuki...