"Tsunagu" is the theme song for the film Shinobi no Kuni starring Arashi member Satoshi Ohno.

The regular edition contains the B-sides "Reach for the sky ~Ten made Todoke~", "Dakishimetai", and "Under the radar", and the instrumentals for all four tracks.

The limited edition contains the music video and making-of for "Tsunagu", the B-side "Oki ni Mesu mama" and its instrumental, and a 16-page lyrics booklet .

"Tsunagu" was used as the theme song for the film Shinobi no Kuni starring Arashi member Satoshi Ohno.

"Tsunagu" debuted at number twenty-four on the Billboard Japan Hot 100 chart on May 29, 2017.