"The first thing I struggled with was the 'biodegradability.'"
"I see."
Biodegradability was the property of breaking down into inorganic substances after disposal without releasing harmful byproducts.
Most plastics remain in the soil or water for long periods without decomposing, making them a major source of environmental pollution. It seemed Saki had put in the effort to incorporate this property after hearing stories about Earth, Jin's original home.
"Since it’s magi-plastic, it won't degrade as long as you're supplying it with mana."
Saki explained that once the mana supply was cut off and the internal mana dissipated, the degradation process would begin.
"That's impressive."
"Ehehe, I can't let Hanna-chan outshine me, after all."
With that, Saki continued her explanation.
"Magi-type metals and alloys are strong because the magi-isotopes they contain react with free ether to increase their strength. I wanted to achieve that same effect with resin."
"That makes sense."
Jin had already deduced that much. The primary challenge had been deciding on the specific molecular structure of the plastic. When he mentioned this, Saki answered with a laugh.
"Yeah. Regarding that, I just flat-out decided that it was impossible for me to do it alone. So, I researched the Magus's books. In the end, I had Marikka-chan help me, and I also consulted No. 700672."
"I see... You really worked hard on this."
"No, no! I'm doing what I love, so even if it's hard work, I never found it painful!"
Saki remained characteristically positive.
"So, I looked into various things. I figured out the molecular structures, but there was no way I could replicate all of them. Besides, I didn't want them releasing toxic gases if they were burned."
"Right."
Saki held firm convictions on the matter.
"I narrowed the candidates down to polyethylene, polypropylene, polystyrene, polycarbonate, polyacetal, and polyethylene terephthalate... Phew, I managed to say all that without tripping over my tongue."
After rattling off the complex names in a single breath, Saki gave a wry smile and stuck out her tongue.
"I don't fully understand all of them myself, though."
"In short, you chose plastics composed only of carbon and hydrogen."
"I understand that much."
From Jin's knowledge, plastics containing sulfur, nitrogen, or chlorine were known to generate toxic gases depending on how they were incinerated, polluting the environment. It was clear that Saki had made environmental considerations her top priority.
"Then, from the candidates I just listed, I selected the ones that could be replicated with Craft Magic. Polyethylene, polypropylene, and polyacetal—those were about the limit."
In reality, the other plastics featured structures called benzene rings, which made them far more complex to synthesize.
"No, even so, it's amazing."
Jin was honestly impressed.
"The one disappointing thing is that all of them have poor transparency."
They couldn't be used as window materials, Saki said, looking slightly regretful.
"But I think you can just make that a goal for the future," Jin offered, trying to cheer her up. After all, it wasn't as if they lacked other transparent materials.
"Yeah... You're right. One step at a time!"
Jin looked once more at the three types of magi-plastic Saki had developed.
Magi-polyethylene. Jin had been just one step away from developing it himself, but Saki had successfully brought it to completion.
Magi-polypropylene. It was harder than polyethylene, which would allow for different applications.
Magi-polyacetal. This was the strongest of the three.
"This is just a guess, but I think they'll last about ten to twenty years under normal use."
"Probably."
The plastics Jin knew from Earth had similar levels of durability.
"But they can be burned, and if you use an ether eliminator, they can be decomposed into carbon, hydrogen, and oxygen!"
"That really is incredible."
One could truly appreciate the hardship and effort Saki had poured into this project.
"So, what did you use for the raw materials?"
This was the hurdle where Jin had hit a dead end.
"Kufu, I used ethenol!"
"Of course!"
Ethenol was a synthetic substance where free ether was dissolved into water made of magi-isotopes. It would contain a massive amount of hydrogen and oxygen magi-isotopes.
"I didn't have much trouble with the carbon."
Magi-isotopes of carbon were found in many things—for example, the meat and hides of magical beasts. They were also abundant in magi-resin.
"So, Jin, what are you going to make first with this?"
"Baby bottles, I suppose."
"Eh?"
Saki's eyes widened at the unexpected answer.
"The number of babies in Kaina Village has increased, and I'm sure there's a demand for them elsewhere too."
"Kufu, but baby bottles, of all things? Now that you have a home of your own, have you started to become a bit more aware of your responsibilities, Jin?"
Saki laughed mischievously and patted Jin on the shoulder.
"Responsibilities?"
"...Good grief. You'll be a father yourself someday, Jin."
"A-Ah, so that's what you meant."
Jin turned red after Saki called him out.
"Anyway, thank you, Saki."
"Kufu. It's for your sake, Jin, but I really hope it helps the world, too!"
"Yeah, I hope so."
Watching Saki smile so brightly, Jin found himself breaking into a smile as well.
＊ ＊ ＊
"So, what have you been working on, Jin?"
Jin and Saki continued their conversation while drinking citran juice in the laboratory's dining hall.
"Well, I don't know if there will be any further trouble with Hale or not, but I've been focusing on the lessons learned from the battle with the Disaster."
"Lessons learned?"
"Yeah. I realized that we don't have a decisive move against giant opponents."
"Ah, certainly."
Since Saki had been with him on the Adriana during the conflict, she understood exactly what Jin meant.
"So, what are you doing specifically?"
"Enabling the Magi Trans Cannon to fire a Mana Explosion, and preparing high-output mana bombs."
"That doesn't sound like a very pleasant development project."
Seeing Jin's face, which looked as if he had chewed on a bitter bug, Saki gave a wry smile.
"Exactly. I want to be free from all this trouble as soon as possible."
"Kufu. I’ll help in whatever small way I can. Do your best, Jin. For Elsa's sake, and for the sake of this planet."
"That goes without saying."
Saki narrowed her eyes and gazed at Jin as he gave his answer.