"Natsu no Hi" (夏の日 Natsu no Hi?) is a Japanese song sung in the background of the TV series Sonic X. This is the first insert song of the broadcast version of the fifty-second episode "A New Start", sung by Off Course during the scene where Amy reunites with Sonic.
- Lyrics and Composition: Kazumasa Oda
- Arrangement: Off Course
- "Natsu no Hi" translates to "Summer Day" in English.
- In the original Japanese version of Sonic X, this song was only heard on the broadcast TV version of the show. This song was replaced with "The Shining Road" for the DVD and online streaming releases.
- Despite being absent in the DVD and online streaming releases of the Japanese version, this song was retained for both the TV and DVD releases of the French dub.