She nodded again. Whether it be helping her with the mortar and pestle, learning how to bandage wounds, or gather herbs, Sen had lately taken an interest in medicine. After grabbing a basket, he followed her down the small path into the woods, one that had been made by healers before her.
"D'you get much ninja to treat?" he asked as he followed her. Sen had become rather curious about her shinobi patients since he'd met Hashirama. "Are most of them like the one that stayed for lunch?"
She shrugged. "They're all a little weird."
"Or a lot weird," said Sen with a laugh.
Her thoughts turned to the ninja that had visited a few days ago. Hashirama had left after thanking her profusely and tentatively asking if he could come again someday. Yui, of course, had assured him that he could. As Sen had remarked, Hashirama was a little strange, but perhaps that was part of his charm. She hadn't met anyone with genuine ambitions in a long time. Not many people could dream when they were preoccupied with survival.
As they stopped to pick leaves and roots, Yui pointed out the names and uses for each one.
"Shiso leaves are for colds," she said, gesturing to a plant tucked behind an oak tree. "The seeds can be crushed to make oil. The wild, weedy ones ain't as good as the one in our garden, but I like taking some anyway."
Sen scampered to grab a few leaves, eyebrows furrowed with concentration.
"Over there is—"
"Burdock!" finished Sen. "The leaves are itchy, right? But the roots are really good for… um, fever?"
Yui smiled. "That's right. And that one over there?"
"Bay leaves!" He reached out to grab some, but Yui pulled him back.
"No, that's rhododendron." She gave him a hard look before pointing to the flowers. "Bay laurel has yellow flowers and light green leaves. Rhododendron has red, purple, and white flowers and dark leaves. It's also poisonous."
Sen cringed. "Oh. Sorry."
"It's fine. Just be careful. Picking the wrong berries or leaves could kill someone," said Yui, gentler than before. "Now, what're bay leaves used for?"
"Headaches?" he wagered.
"Stomach aches. They're also good for pregnant women."
They continued in silence for a while longer. Sen seemed to be glancing over every few seconds. Clearly, he had something on his mind. She'd wait. If it was important, he'd tell her. She brushed the dirt off the burdock root and sighed. Yui would kill for a fully stocked medical cabinet.
Most of these herbs did have medicinal properties. The problem was concentration. Back in the modern world, the components that did the healing were often isolated and distilled to increase potency. Willow bark contained salicin, a chemical compound that could be synthesized into acetylsalicylic acid, more commonly known as aspirin. Back in her original world, there had been ongoing debate about the efficacy of medicinal herbs. Sometimes, it wasn't possible to isolate all the complex interactions between compounds, and medicine didn't like not knowing.
That debate had no relevance now, of course. Here, Yui could only use the raw plants and hope for the best. She paused in front of an oak tree that she collected bark from. Unfortunately, she had no idea how to isolate salicin or aspirin. In comparison, the story and process of penicillin was well known. It had a low success rate due to the finicky nature of the fungus and the resulting low production, but the basic method could be done. On the other hand, no one really knew or cared about aspirin. It had been synthesized more than a hundred years ago and was ubiquitous the world over.
