Summertime by Bridgit Mendler

Another summer song from  the fantasy film  Arrietty, titled The Borrower Arrietty (借りぐらしのアリエッティ Kari-gurashi no Arietti?) in Japan and The Secret World of Arrietty in North America, is a 2010 Japanese animated fantasy film directed by Hiromasa Yonebayashi and scripted by Hayao Miyazaki and Keiko Niwa. It is based on The Borrowers by Mary Norton, an English author of children's books, about a family of tiny people who live secretly in the walls and floors of a typical household, borrowing items from humans to survive.

Here you can see the trailer of the film