"Heartbeat (Tainai Kaiki II) – Returning to the Womb" is a song resulting from the collaboration between Ryuichi Sakamoto and David Sylvian,[1] with music co-written by Arto Lindsay.

[2] The mini-album containing the track was released in 1992 and features a previous collaboration between Sakamoto and Sylvian, the 1984 re-recording of "Forbidden Colours", produced by Steve Nye, that was the B-side to Sylvian's single "Red Guitar" and features as a bonus track on his 1987 album Secrets of the Beehive.

The song can be found on Sakamoto's album Heartbeat,[3] in different versions depending on the issue as well as in Sylvian's compilation A Victim of Stars 1982–2012 (CD 1).

The song was included on Sakamoto's album Heartbeat original Japanese issue in a version without Sylvian's lyrics and vocals (only sung by Lindsay).

[6] "Tainai Kaiki" was said to be "a neatly crafted pop song, mournful enough to appeal to Sylvian fans".