The True Identity…!! (その正体…!!, Sono Shōtai…!!) is chapter 381 of the original Naruto manga.
Jiraiya, despite severe injuries, manages to capture one of the Six Paths of Pain. He tries to figure out why none of the six resemble Nagato, one resembles Yahiko, and all have Rinnegan. Seeing that the Pain he captured has a scar on his forehead, Jiraiya recognises him as a ninja he faced in the past. Knowing for a fact that this isn't Nagato, Jiraiya decides to test a hunch rather than return to Konoha. He asks Two Great Sage Toads to go home, but they refuse. He is at least able to convince Shima to take the Pain he captured to Konoha for study. Jiraiya and Fukasaku faces the remaining Pains and Jiraiya confirms that he met all of them before. He figures out the secret of Pain, but he is surrounded and his throat is crushed.