WARNING: The following contains spoilers for Season 1, Episode 15 of Dr. Stone, "The Culmination of Two Million Years."
The last episode of Dr. Stone ended with Chrome pulling off a dramatic win against the village bully, Magma, in the quarter-finals of the Grand Bout -- the tournament that will determine priestess Ruri's husband and the new village chief. Given that the final two competitors Chrome will have to face are his Kingdom of Science comrades, Senku and Ginro, Chrome's victory seemed assured.
Or, at least, it was assured until the worn-out science apprentice collapses from exhaustion at the start of Episode 15. This makes Senku -- against all the odds -- the actual winner of the Grand Bout following his easy win against Ginro in the semi-final match. Suddenly, Senku finds himself a married man. As he decries his fate, many of the villagers -- including Ruri's father -- are none too pleased about an outsider becoming their new leader, either.
As always, though, Senku quickly finds a modern solution to his Stone World problem. When the villagers bring out their stash of wine to celebrate the new union -- as is tradition -- Senku swiftly announces that he'll be divorcing his new bride and makes off with as much of the alcohol as he and his acolytes can carry, leaving the villagers to assume that he's gone "utterly insane." This alcohol isn't to have his own private party with, of course, but to use the liquid to finally complete the cure-all drug he's promised to heal Ruri with.
With all of their materials and ingredients in place after six months of hard labor, Senku gets Chrome, Kohaku, Suika, Kaseki and Gen to work on the complicated 25-step process. It takes them most of the night but somehow, and to Gen's utter delight, Senku also finds the time to throw together carbonated water, cilantro, lime and honey caramel to fulfill the promise he made to Gen in exchange for his defection from Tsukasa's Empire: a bottle of Cola.
While the Mentalist gleefully enjoys his drink, Senku administers the white powder to Ruri. At first, the priestess appears to take a turn for the worst and her father accuses Senku of poisoning her deliberately. But, as Senku points out, this is actually a good sign. At first, he'd worried after his examination of her that she may have tuberculosis, which the drug would be ineffective against. Seeing the infection fight to defend itself, however, means that she's actually suffering from pneumonia, which is well within the drug's remit to cure.
With further doses, Ruri is indeed fully cured of the life-threatening disease and, as a show of gratitude, her father passes his title onto Senku. It's during this handover ceremony that Senku learns the name of the village he's just won the governorship of, Ishigami Village, which is significant because "Ishigami" happens to be his surname. Adding to his shock, Ruri informs him that she's "known about [him] for some time."
Now, the biggest mystery in Dr. Stone's world is how a village established long after Senku became trapped in stone came to bear his name. As one arc of Dr. Stone's story comes to a close, a new one begins with the promise to further explore the Stone World's emerging mysteries.
New episodes of Dr. Stone air every Saturday night as part of Adult Swim's Toonami block and are available on Crunchyroll.