o/a
A 2009-2012 crude humor comedy manga by Watarai Keiji. O/A is short for Operation Aurora.
The series revolves around the idol Horiuchi Yutaka and aspiring comedian Tanaka Harumi. At the start of the series Yutaka gets a gig as the host of a late night radio show once a week. Due to circumstances, Yutaka ends up unable to host during part of her first show. Desperate on what to do, the staff realize that the part-timer Harumi sounds just like Yutaka and forces her to host the show in Yutaka's absence. This coincidence would eventually lead to both girls co-hosting the show while not revealing to the public that there is more than one host.