Buddies Back to Back (背中合わせの仲間たち Senaka Awase no Nakama-tachi) is the twelfth episode of the Dr. Stone anime.
Senku must gather the most difficult material to obtain when compounding the cure-all drug: Sulfuric Acid. The Kingdom of Science discovers a pool of this material, and knowing the risks involved, Senku hatches a plan to obtain it.
As he promisedm Senku creates a silver spear, using native silver, a mineral Chrome had mistaken for some kind of plant roots. Happy, Ginro monologues and even taunts his brother. Kohaku shuts up him up while Senku explains they need it to get the maximum danger materials. They finish the silver spear and Senku reveals that Ginro must be the team's bodyguard.
Senku, Chrome, Kohaku, and Ginro walk past the hot springs, and Senku reveals the silver spear is actually a sensor. If it turns black, that means danger is imminent and the holder must flee immediately or die. Senku says their opponent will kill them after just one mistake and this is the greatest hurdle to making sulfa drugs.
The group ends up at a river without a single fish and moves upstream from there. Ginro is too scared to fulfill his job as a bodyguard and walks far behind them. Senku and Kohaku make him walk ahead of them until they end up at a large pool of what appears to be an emerald green spring. Beautiful at first, Ginro walks toward it until his spear reacts to the hydrogen sulfide and turns back.
Senku yells at Ginro and Kohaku saves him in time before the gas kills him. This makes them all realize how deadly the spring actually is. Senku explains to everyone that the spring is made from Sulfuric Acid. They return to base and try to develop a plan to get the material. Kohaku wants to try and use her speed to quickly gather it, but Senku quickly debunks that, as people have been killed in an instant by the gas.
To properly fight the chemicals, Senku gets Kaseki to craft gas masks. Senku tells Chrome that he can't come with him to get the acid. The gas masks aren't a guarantee and Senku says he can't let both of the scientists die. He wants to pass down all his knowledge to him, but Chrome outright refuses. He refuses to allow Senku to put his life on the line unaided and promises to drag him back alive. They agree to raid the poison gas together after Chrome argues his point that with him as support, Senku has a migh better chance of surviving after an accident.
Kohaku recalls her father trying to get Ruri to pass down her knowledge to her. Kokuyo had planned to make Kohaku her successor but she refuses to accept a plan that's okay with Ruri dying. In response, she decided to become unworthy of becoming a priestess, determined to upset their father. Drawing the parallel in her head, Kohaku decides to tease Chrome by suggesting he marries her instead, since Ruri will be taken and they look similar. Chrome turns down her offer, bringing up their personalities are too different, and calling her a gorilla once again; he is promptly punished, but he retorts saying that she just proved his point.
Senku shows everyone how to make gas masks and the duo of scientists prepare to move out. They leave without the cowardly Ginro, taking his spear with them. The blackened spear is turned back into shiny silver by cleaning it with an alkaline, and they return to the poison spring. They put their faith in the gas masks and try to act quickly. They can't freak out and waste their air, yet even Senku is slightly nervous.
Kaseki encourages Ginro to face his fears and embrace them because that's what keeps humans alive. No one is immune to fear, not even his brother Kinro. The old man gives Ginro the last gask mask and he's inspired to help save Ruri despite his fear.
Meanwhile, disaster nearly strikes when Senku's air hose is damaged by some drips of acid that splashed on. Chrome warns Senku, and he quickly takes care of the issue. As this is happening though, the exhaltated Chrome stepped on a weak spot in the bank of the lake. It crumbled, sending Chrome on his way to a deathly plunge. Senku runs after him, though from where he was he would never make it in time. Ginro arrives in the perfect moment to save Chrome from certain death. Chrome grabs on to Ginro's spear, but he's still too afraid to control his breathing and can't pull Chrome back to safety. Senku reassures him that they can win against nature if they use their hearts and mind.
Inspired, Ginro overcomes his fear and helps Chrome get back to a safe area. Together, the trio manages to obtain sulfuric acid.
- Gas Mask
Anime to Manga Differences
- A dialog mentioning about "hair-like things" is changed from Kohaku to Chrome.
- When telling about the 100 Tales, there are no background images about the story in the anime.
- There's no blunt faces of Kohaku and Chrome when they talk about marriage in the anime.