Reincarnated as the Heroine’s Big Sister, but My Little Sister Fell for Me Instead - Chapter 9

A month had passed since my joint research with Edvard began.

We met twice a week in the library basement. A comparative structural analysis of light and dark attribute interference magic—that was the nominal theme. In reality, our discussions had broadened. The history of attribute magic, theories of spell construction, and so on. Edvard’s knowledge was vast. Regarding my unique theories, he neither criticized nor affirmed them outright, but sought to verify them. Collaborating with someone like that was comfortable.

Lian continued to come as usual.

For the first week, she seemed to be observing from a slight distance. Her chair was positioned a bit farther away, and the angle of her book was more upright than usual. It was unclear whether she was being cautious or simply trying to acclimate to a space with someone other than me.

I said nothing.

From the second week, her chair returned to its original position. Whether she had let her guard down or simply grown accustomed, I still couldn’t tell.

Today was not a day Edvard was scheduled to come.

Lian and I were alone, each reading our own books. It was raining outside. The sound of rain didn’t reach the library basement, but the air felt damp and heavy. The dark purple lighting seemed closer to orange than usual.

“Sister.”

“What?”

“Are light magic and dark magic truly paired opposites?”

I looked up from my literature. Lian had placed her book on her lap and was looking at me.

“I overheard your conversations with Edvard, so I was curious.”

“You were listening?”

“I could hear you. I wasn’t intentionally eavesdropping, though.”

That made sense, I thought.

“I’m not sure if ‘paired opposites’ is entirely accurate. ‘Mirror images’ might be closer.”

“Mirror images?”

“Light attribute interference magic expands magical energy outward. Dark attribute converges it inward. They share the same starting point, but their directions are opposite.”

Lian thought for a moment. “If they’re opposites, but originate from the same point—”

“You could say they’re connected.”

Lian looked at me.

“Connected.”

“In theory. There’s almost no literature on what actually happens when light and dark attribute magic interfere with each other. That’s why Edvard and I are investigating.”

“Will you conduct experiments?”

“We’ve discussed doing so eventually.”

Lian fell silent again for a moment. In the windowless basement, only the sense of rain lingered.

“What exactly would an experiment involve?”

“Well… It would require physical contact, particularly contact between areas close to each other’s mucous membranes, to facilitate magical energy transfer.”

Instantly, Lian’s expression clouded. Then, as if sulking, she turned her face away.

“And you would do that, Sister? With Lord Edvard?”

“That would be the case.”

Silence hung between us for a while. Lian fiddled with the hem of her clothes.

“Could you try it with me?”

“…Try what?”

“The interference experiment. Between light and dark attributes. I can use light magic, after all.”

I didn’t answer.

Lian’s offer was simple. It was merely a proposal to serve as a research subject. But something within me hesitated.

I considered the implications of allowing my dark magic to interfere with Lian’s. Magical interference involves the mingling of the casters’ magical energies. There’s no pain, but one receives a sensory impression of the quality of the other’s magic.

“I’ll discuss it with Edvard.”

“Was that a rejection?”

“It’s just on hold for now.”

Lian gave a small smile. “Isn’t that the same thing?”

“…Perhaps it is.”

When I conceded, Lian smiled a little more. When she makes this face, she looks her age. For a first-year, she often seems oddly composed, so seeing her smile is somewhat reassuring.

“Sister,” Lian said. “What do you think of Lord Edvard now?”

“You’re asking again?”

“I’ll ask as many times as it takes.”

It was the same question as a month ago. But the way she asked had changed slightly. Last time, her voice sounded probing. This time, it was a bit calmer.

“I consider him someone I can talk to as a fellow researcher.”

“Is that all?”

“That’s all.”

Lian nodded. She didn’t deny it. Despite asking “Is that all?”, she wore an expression that seemed satisfied with that answer.

“I understand.”

“Understand what?”

“Just a feeling.”

It was a vague reply, but I didn’t press further.

After a while, Lian opened her book. This time, she began reading properly. The sound of turning pages returned.

I also returned to my literature.

While looking at the interference magic spell diagrams, I thought about Lian’s offer. If I only considered the surface meaning of her words—to be a test subject—there was no reason to refuse. Edvard would likely agree as well. An interference experiment with a Saint candidate possessing the highest purity of light attribute magical energy would hold significant research value.

But.

My dark magic touching Lian’s magical energy.

When I imagined that sensation, it wasn’t just hesitation I felt. It was something else I couldn’t quite put into words. It wasn’t that I didn’t want to touch it. If anything, it was closer to the opposite.

Because I had a vague feeling it wasn’t a good idea, I put it on hold.

“Sister.”

“What?”

“About what we discussed earlier, I wouldn’t mind if you refused,” Lian said, still looking at her book. “But I’d prefer if you didn’t refuse.”

“…Which is it?”

“Both. I wouldn’t mind if you refused, but I’d rather you didn’t.”

I fell silent for a moment.

“You’re being selfish.”

“I can only afford to be selfish in front of you, Sister.”

I couldn’t say anything more after that.

For a while, I pondered the reason why I couldn’t.