Following the Steam release of Bullet Soul in April, 5pb. has announced that it will release shoot 'em up Bullet Soul: Infinite Burst for PC via Steam on July 31. It will cost $14.99 plus a 20 percent discount at launch (or a 30 percent discount if you already own Bullet Soul).
Source: Bullet Soul: Infinite Burst coming to PC via Steam on July 31 - Gematsu