"Star Seed" (カクセイ, Kakusei)[a] is the debut Japanese single by the South Korean girl group Loona.

It was released on September 15, 2021, through Blockberry Creative, Mercury Tokyo and Universal Music Japan alongside its A-side "Hula Hoop".

[3] In the same month the company announced that the group will be having their official Japanese debut in September.

[5] The song is written by Sumire Yoshida (Suu) of Silent Siren and is composed by Naoki Kubo.

In addition, a solo jacket version of each member will be released exclusively for Universal Music Store.