Dr Stone: 10 Inventions With the Least Plot Relevance, Ranked

Credit:- TMS Entertainment

The anime adaptation of Dr. Stone is finally nearing its end. Throughout the anime, Senku Ishigami has reinvented many pieces of modern technology to advance the Kingdom of Science. However, the sheer volume of scientific creations means not all inventions maintain long-term relevance.

So, let’s rank the ten inventions based entirely on their overarching plot relevance. There are items that were used just once or twice, but had relevance in the overall story, and there are also items that could’ve easily been replaced by anything else. Let’s dive in.

TITLE	Dr. Stone
STUDIO	TMS Entertainment
MAL RATING (as of April 18, 2026)	8.26 / 10
IMDb RATING (as of April 18, 2026)	8.10 / 10
ORIGINAL CREATOR	Riichiro Inagaki
RELEASE DATE	Jul 5, 2019
STREAMING	Crunchyroll

10 The Playing Cards Existed Just For Fun

The playing cards were created specifically to play a game of poker in order to make an important decision. When the Science Kingdom was making its way to the United States of America, Senku and Ryuusui couldn’t decide on a route. The ship could either take a long route and arrive safely at the destination, which is what Ryuusui wanted, or it could take a shorter route and arrive early, which is what Senku wanted.

The decision was made through a game of poker, in which Senku won. However, the playing cards never came up again. In fact, the entire game could’ve been any other game, so the playing cards weren’t relevant at all.

9 Dragos Never Came Up In Story Again

Dragos represents the fiat currency introduced by Ryuusui to establish a functioning economy within the Kingdom of Science. Despite it being a very important element in any kingdom, we rarely see it being used at all. That is primarily because Senku and others don’t need to buy anything; they own it.

The last time it was seen was when Ryuusui brought materials from Barcelona.

8 Gas Masks Were Used Only Once

The gas masks were reinvented by Senku to counter a specific environmental hazard: the hydrogen sulfide gas surrounding the sulfuric acid lake. Securing sulfuric acid was a mandatory step for the creation of sulfa drugs, which were important to cure Ruri at the time.

The masks functioned exactly as intended, protecting the lungs of the characters during the retrieval mission. However, following this single expedition, the masks were stored and never utilized again. There were many scenarios where they could’ve been used, for example, when working in mines. While the gas masks were crucial at the time, they stopped being relevant right after.

7 Water Carbonator Existed For Just One Reason

The water carbonator was reinvented to infuse water with carbon dioxide. Its existence in the story is entirely for the production of a single item: cola. This Water Carbonator was manufactured by Kaseki, the artisan of the Ishigami village, in a way that it used the force from flowing water instead of Electricity.

It was probably based on the original design by Joseph Priestley. However, after making cola, it was never seen again.

6 Senku Made Cola For Gen, That’s It

Senku made Cola for a very specific reason. Gen Asagiri was working for Tsukasa at the time; however, he wasn’t as loyal as he seemed to be. Gen had only one goal: if there was a place or faction that would allow him to live comfortably, he would be there.

Gen asked Senku a simple question, “Can you make cola in the Stone World?”, to which Senku agreed. After that, the Water Carbonator was used to make the cola, which was the final straw that made Gen Asagiri join the Kingdom of Science. However, we never saw Cola again.

5 Millet Flour Was Too Horrible To Be Eaten Again

Senku took the help of Kohaku and successfully recreated the Millet Flour in the Stone World. Prior to that, the people of Ishigami Village were eating nothing more than the fish they were catching, and hence, their food did not last long. Senku created millet flour, which can be stored for a long time, but it tasted horrible to him.

However, for the people of the Stone World, who had eaten nothing but unseasoned meat and fruits here and there, millet flour was a godsend ingredient. It didn’t take long before Senku invented more food; hence, millet flour was never brought up again.

4 Ramen Cart Existed Only For Ishigami Village

Following the invention of Millet flour, Senku immediately invented Ramen in the Stone World. A whole Ramen cart was then put together, so that he could attract the attention of the people of Ishigami Village. His goal was simple: make them eat, and then make them work. It was also that since they had eaten nothing like Ramen ever before, they were more likely to join his side.

However, Senku never replicated this strategy anywhere else. Despite encountering other groups and factions later in the story, the concept of a mobile food cart was never utilized again. In fact, a ramen cart could’ve been replaced by anything else as well.

3 Electrostatic Generator Could’ve Been Used More

The electrostatic generator is a device that creates static electricity. It was introduced very early in the very first season of the anime and used primarily to demonstrate the concept of electricity to individuals who lacked modern scientific knowledge.

Senku used it to assert dominance over Chrome, who boasted of being a sorcerer. To people who had never experienced electricity before, this appeared to be true sorcery. It helped Senku gain the trust of more people. However, the same strategy was never used again. In fact, it could’ve been used to scare some of the strongest characters in the story.

2 Soap Bubbles Used To Fake Magic Just Once

Just like the Electrostatic Generator, Soap Bubbles were also used to show what Senku was capable of. He created the soap bubbles using a bit of water and the soap he had invented long ago with Taiju, and amazed Kinro and Ginro, the two bodyguard brothers of the Ishigami Village.

This was very effective against the people of the Stone World; however, the same tactic was never used again, even when Senku encountered more primitive people in another village. I would’ve loved to see the reaction of Ibara if Gen lied to him about the bubbles being something really scary and harmful.

1 Cotton Candy Could’ve Won More Hearts

The cotton candy machine was built to produce spun sugar. Similar to the ramen cart, it was utilized as an instrument of psychological warfare against Homura, who was working for Tsukasa. Senku used the cotton candy to appeal to Homura, a key spy from the Tsukasa Empire, successfully earning her favor by providing a high-value luxury item.

This could’ve been used even more times, because who doesn’t love sugar? However, the anime never brought it up again, other than the time when the machine was used to make wires instead of cotton candy.

RANK	INVENTION
10	Playing Cards
9	Dragos
8	Gas Masks
7	Water Carbonator
6	Cola
5	Millet Flour
4	Ramen Cart
3	Electrostatic Generator
2	Soap Bubbles
1	Cotton Candy

Let’s be honest, just because these inventions didn’t turn out to be that relevant, doesn’t mean they were useless. The cotton candy was important to win the heart of Homura, the soap bubbles were necessary to assert dominance, the gas masks were crucial to protect the characters, and without cola, Tsukasa could’ve known that Senku isn’t dead.

There are many more inventions in the anime Dr. Stone, but not all can be as significant as, let’s say, Nitric Acid. Perhaps, we will see even more amazing inventions in the upcoming episode, Episode 28 of the final season, that is releasing on April 23, 2026.

What are your favorite inventions from Dr. Stone? Let us know in the comments.

Dr. Stone is streaming on Crunchyroll.