Shinzo Abe dropped 57 gold coins, 75 XP, and three brass tubes
Most JRPGs don't end until you kill God, so he's got a bit of work to do and a party to recruit.
After killing Shinzo Abe, the sky starts raining blood and the Protags plucky cartoon mascot friend realizes that the mastermind behind all the twisted desires in Japan is that the false god, the Demiurge (AKA Yaldabaoth of Gnostic fame) has been controlling our desire for positive change this whole time. He is now combining the world of people's collective consciousness with reality, so people can be well and truly under the thumb of his zealotry and give up their hopes of a future and instead live as slaves to him.
The protag and his friends go to fight this god, and when all hope seems lost, the protag summons a giant demon (the ultimate symbol of rebelion against god) to shoot the Demiurge in the head. Thus saving humanity and giving people back their desire to change the world for the better instead of praying to a false god.
And then a special edition comes out and ruins this message of proactive change, or some shit idk.
The REAL final boss is the president of the United States. Be careful, he tends to use nuclear weapons and that is an insta-death/game over attack.
the doohickey is a unique drop currently located in the NPA headquarters dungeon
the raid is yet to be attempted, not because of any final boss, but because the mob waves are levelled much higher than usual dungeons and their spawn rate is unmatched
He should be released from prison to do one last job, then he's done for good.