It features the participation of various South Korean songwriters and production teams such as KZ, Kim Seung-soo, Nthonious, KCKT, Ryan S. Jhun, Andrew Choi, and others.

It made the group became the seventh artist that managed to sell over 300,000 copies in the first week with a debut single according to Oricon.

[1] On January 14, it was revealed that the group's debut EP single was titled Protostar and would be released on March 4 with "Infinity" as the lead track.

[19][20] On June 21, JO1 performed songs from the single in KCON:TACT 2020 Summer, making them the first Japanese boy group to ever participate in the convention.

[21] Shortly after its release, Protostar peaked at number one on iTunes's real-time album charts in five regions in addition to Japan, such as Hong Kong and Taiwan.

[25] It subsequently ranked third on the monthly chart,[26] and received a Platinum certification by the Recording Industry Association of Japan for shipments of more than 250,000 units.

[27] Protostar eventually ranked sixth on Oricon's mid-year chart,[28] and tenth on the Combined Singles Sales category.

[31] Protostar also debuted atop Billboard Japan Top Single Sales,[32] and ranked eighth on the mid-year edition of the chart.