Compared to Water Breathing, Tanjirou, whose ancestors had been selling charcoal for generations, was clearly more suited to Flame Breathing.
In the original timeline, the four members of the protagonist group were all at least of Pillar-level strength by the age of fifteen, and none of them had poor talent.
Tanjirou was even more outstanding. When using Water Breathing, he was at most a decent swordsman, but when he first used Sun Breathing, he was no match for Lower Moon Five.
However, from the moment he started using Sun Breathing, which was more compatible with him, Tanjirou's strength grew explosively. He consecutively participated in the slaying of Lower Moon One, Upper Moon Six, and Upper Moon Four, and in the process, became the first person to awaken the Demon Slayer Mark, and his output in the team became increasingly high.
Eventually, when he unlocked all three abilities in the Infinity Castle, he was practically a mini Yoriichi.
Flame Breathing is more compatible with Tanjirou.
In the first half-year of following Kyojuro Rengoku, Tanjirou's strength was actually enough to pass the Final Selection, but Kyojuro, wanting to be cautious, made Tanjirou wait another half-year.
As a result, after a year, Tanjirou had already reached the point of trying Constant Total Concentration Breathing.
Even if he hadn't fully mastered it, in terms of strength alone, the biggest difference between him and the lower-ranked swordsmen of the Otsu and Hei ranks was only practical combat experience.
After passing the selection, because his Nichirin Blade had not yet been forged, Tanjirou, after visiting his sister, thought about returning to his hometown to pay respects to his deceased parents and siblings, and temporarily stayed at the Fuji House.
"Tanjirou! Can you come help? Pillar Kocho and Pillar Shinobu have arrived, and they brought a lot of flowers and soil to move into the yard."
An Invisible, completely covered in brown-black cloth, called out to Tanjirou for help.
The enthusiastic Tanjirou naturally agreed.
"Eh? These flowers..."
"We found them near your house, Tanjirou. Last night, Shimizu and I chased a demon to the mountain where your house is located, and finally, at dawn, Shimizu led me to these flowers, so we decided to bring them back to the Butterfly Mansion and cultivate them ourselves," Shinobu Kocho said with a smile on her face.
"This blue flower..."
Tanjirou looked at the sky.
Everyone turned their gaze to Shimizu.
Making a lamp that can emit sunlight at night...
If that were used to deal with demons...
"Shimizu... is that really possible?" Shinobu Kocho hesitated.
"Why don't we try it with a flower? We can use a room for the experiment," Shimizu said.
Several Invisibility members hurriedly cleaned out a spacious room.
Yesterday, while passing through Tochigi Prefecture, Shimizu received some items that he had previously ordered from his uncle, Uesugi Sakai, at the post office there.
Those were materials for making a sunlight lamp.
The Taisho era was still decades away from mankind inventing the sunlight lamp.
But the Avatar of the DC world spent twenty million US dollars to buy a factory that produced furniture lamps and lanterns, and according to the production methods in the factory, developed a sunlight lamp that could be manufactured in the Taisho era.
That thing already had finished products in the DC world, although the effect was far worse than the household lighting and agricultural greenhouse sunlight lamps that were sold as commodities, it could indeed light up with white light.
According to spectral analysis, the wavelength combination of each band of this lamp's light is close to sunlight.
If Aoba Kuzuhira in the 21st century could use sunlight lamps to cultivate Shimizu's Spider Lily, then this one should also work, at most the effect would be worse.
As for whether it could cause harm to demons, Shimizu felt that it should be possible, but the effect would definitely not be as good as real sunlight.
Previously, Shimizu had also created simpler ultraviolet lamps according to the methods provided by the DC world avatar, and had specifically controlled demons during missions to conduct irradiation experiments.
There was an effect, but it only made the demon's skin feel slightly burning, the body felt slightly weak, and the regeneration speed was reduced slightly.
It was not much different from wisteria flowers, possibly because the light intensity was insufficient, but if the ultraviolet light was too strong, it would also cause great harm to the human body.
Shimizu carefully took out a glass tube.
This was not an ordinary glass tube.
But a vacuum tube filled with mercury vapor and inert gas.
The boiling point of mercury is degrees Celsius, but in a vacuum environment, due to the reduction of pressure, liquid molecules will actively escape and turn into gas due to the change of vapor pressure and external pressure.
As for inert gases and vacuum tubes, they had already been invented and extracted by humans in the Taisho era.
In 1898, neon, krypton, and xenon were extracted from the air. In 1904, the vacuum tube was invented by John Fleming, who discovered the classic right-hand rule, and in the same year, Ramsay, who discovered and extracted inert gases, won the Nobel Prize.
However, although they already existed, they were really not easy to obtain in this era. Shimizu could only ask Uesugi Sakai to use his connections to order a few lamp tube samples from England.
The two ends of the vacuum tube were metal electrodes, and the inside of the tube was coated with a phosphor, used to replace the fluorescent powder that could not be prepared in this era.
Shimizu took the spare power supply from Yoriichi Type One's hand and connected it. Finally, he took out the prepared inductor coil to replace the ballast.
After everything was assembled, Shimizu reached out and pressed the switch.
The sizzling sound of electricity rang out, and Shinobu Kocho and Tanjirou, who were standing behind Shimizu, didn't dare to breathe.
The next second, a slightly dim, yet pure and holy white light illuminated the dim hut.
At this moment, a loud cry came from the entrance of the Fuji House.
"Is Tanjirou here? I am a swordsmith from Swordsmith Village, here to deliver your sword! Eh? This soil in the flower pot... did you discover a new Scarlet Iron Sand ore?"
Shimizu suddenly raised his head and got up to open the door of the hut.
He saw an old man take off the Hannya mask, dip a pinch of red soil with his finger, and try it in his mouth.
"Scarlet Iron Sand... solar energy... sunlight lamp..." Shimizu murmured, looking at the sunlight lamp surrounded by everyone.
At the same time, in the DC world.
At the mayoral election site.
Shimizu applauded, watching Hamilton, who was standing on the podium in front, with one hand on a copy of the American Constitution, solemnly swearing to the citizens with the oath administrator.
