Like last time, Ryuk the death god goes to a hyper intelligent teenage boy and gives him the Death Note, asking him to become Kira again. Protagonist goes "it's the modern day of 2017, you will get caught easily now with cameras and tracing etc". He asks 2 questions - 1) can other people see Ryuk? (yes if they touched the book before) and 2) how far away can you go from me? (about 14 km). Protag says to give him 2 years to come up with a plan, then come back and give me the Death Note.
2 years passes, Ryuk shows up again. Protag goes "great, I'm going to sell the book" and gets Ryuk to write a message on pen and paper and go to a television station 11km away - it's up for auction, use twitter hashtag and bid. People from the original series who touched the book see Ryuk, so it becomes clear that it's real. Because he's using Ryuk as a proxy message deliverer and Ryuk writes the messages, they can't trace protag at all. Eventually bidding goes up to the international level, with Xi Jipeng, Trump, Shinzo Abe, Putin etc all bidding to obtain the Death Note. Trump wins it with a quadrillion dollar bid.
Protag then has Ryuk broadcast the message to Trump that he is to equally divide the money and deposit it into every account in Japan's major bank whose owner is age 60 and below - this works out to about 10m yen per person and several hundred thousand accounts - impossible to trace. Protagonist wins, all the authorities that caught Light in the original series are completely defeated, they have no way of figuring out who it was, and a few days later the new Kira would be living their life with 10m yen in the bank, no different than anyone else. Protag gives the note to Ryuk, tells him to deliver it to Trump and to never appear before him again - he wants to enjoy his life with 10m in the bank and go back to normal.
There is only one small problem - Protagonist played the death gods so hard that the king of the death gods reeeeees and retroactively writes in a new rule. Anyone who buys or sells the Death Note will die upon taking the note or receiving money as payment. Trump in a 4D chess move lets Ryuk keep the Death Note, so he never received it, but pretends to the world that he still has it, and will never ever use it to boost his ratings. Ryuk, being a rules lawyer and being told "never appear before me again" doesn't tell the protag about the new rule change, when he withdraws cash from his account, he dies of a heart attack.
Final page shows Ryuk writing the oneshot protagonist's name alongside Light Yagami's in the Death Note, with Ryuk acknowledging him as Lights equal.