Natsuki was checking his footing roughly every three steps to avoid stepping on the moss. The ground surface of the Suishin Treesea was complex. He had to navigate carefully between the edges of luminescent moss, the gaps between tree roots, and exposed stones. At first, Lilith had given detailed instructions like "not there, to the right," but now both of them walked in silence. It had been about thirty minutes since Lilith said they should look for Tio. Since then, there had been no real conversation. Lilith walked two steps ahead of Natsuki. Her wings weren't moving completely yet—the charred left half fluttered just slightly behind, and that small lag had been bothering him at the edge of his vision the whole time. (What kind of person is Tio, anyway?) He'd heard Tio was a mage who independently researched tree-pattern magic. That he was also investigating the Black Root Cave. When Lilith called him an "acquaintance," there had been a pause that caught slightly. It seemed like there was a hesitation in her words for someone who was just a casual acquaintance. But he didn't ask. He thought there was no need to ask. Lilith's pale green hair ahead of him glimmered faintly in the light filtering through gaps in the canopy. In that moment, Lilith stopped. "Natsuki-san" Her voice was low. Not her usual bright tone, but one step lower—a cautious voice. Natsuki stopped as well. Lilith crouched down and placed her hand on the ground. He could tell she was using plant sensitivity—an ability moss-winged fairies possessed to understand the state of trees or transmit commands by touching plants. Her small hand pressed flat against the ground, her eyes narrowing. He waited a few seconds. Lilith's complexion changed. "Below. There are things below." "Below?" "A swarm of rot-moss insects. Moving through the earth. Quite a number—" Before she could finish. The ground made a sound—*guzutto*. It was less a sound than a sensation. Multiple vibrations transmitted through the soles of his feet. Not rhythmic, scattered randomly. Dozens—no, hundreds of things moving simultaneously underground. Natsuki instinctively lifted his heels. The moss on the surface bulged in several places. The next moment, heads covered in chitin broke through the soil. Rot-moss insects—magical creatures about fifty centimeters long that inhabited the Suishin Treesea, ate bark, and could devastate forests in swarms, as Lilith had told him—appeared one after another on the surface. One would be fine. Just a big bug. Fifty of them became a "landscape." All around them, things writhed. "Lilith!" "I know!" Lilith pressed both hands deep into the ground. She was sending commands to the roots underground. Natsuki couldn't see it, but the ground responded by swelling upward, and tree roots broke through the soil and rose up. They were forming a makeshift wall. A large root arced upward and stood before the rot-moss insects. The swarm hit the root and stopped—for just a moment. The next instant, the weight of the rot-moss insects made the root creak and groan. Natsuki lowered his backpack and looked inside. His hands moved on their own. Coffee grinder, filter, two ceramic cups, a can of beans, a small kettle for boiling water—none of it would help even a millimeter in this moment. (Fire? Lilith said dryness was their weakness, but is there anything I can use to start a fire—) He didn't have a lighter. No matches either. And he was supposed to be a café manager. "Is there anything I can do?" "Don't move right now! If you move, you'll be stepped on!" It was sound logic. Completely sound. The rot-moss insects were closing in while surrounding them. There were no gaps. If he moved, he'd end up on top of the insects. Natsuki stood perfectly still, holding his backpack. There was nothing he could do. He picked up his backpack again and looked at Lilith. Fatigue was showing on her face. The strain of continuously sending commands to the roots was severe. Her charred left wing trembled faintly. Another root snapped. *Crack*—the sound came, and part of the swarm tried to climb over the broken wall. Lilith bit her lip. She tried to raise the next root— Only one remained. Natsuki became acutely aware of his own helplessness, with no room for excuses. There was nothing he could do in this situation. A café manager who came to another world couldn't fight, couldn't use magic, and everything he had was useless. He just stood there. As the last root groaned like it was screaming and began to break— Wind came from above. A single gust descended from the direction of the canopy, making the moss on the surface ripple as it struck the swarm of rot-moss insects. More than wind—a vortex. A spiraling current of air swept through the swarm of insects, and a radius of about five meters became empty in an instant. The remaining rot-moss insects scattered and fled. Silence returned. Natsuki stood in a daze. Lilith stopped sending commands to the roots and barely managed to keep herself from collapsing to her knees. An awkward silence fell between them. Lilith looked at Natsuki. She started to offer thanks—then realized Natsuki hadn't done anything—and just kept looking at him. Natsuki looked back at Lilith. "...I didn't actually do anything." Lilith said nothing. She didn't deny it. The two of them stared at each other for a while. The rippled moss slowly settled. *** "It's wind-type tree-pattern magic." Lilith said this as she stood up. Her voice trembled slightly. "It's effective against roaring-mist beasts too, and is often used to scatter mist-type magical creatures—but there aren't many people in this treesea who can use a technique of that scale against rot-moss insects of that number." A figure emerged from behind a cliff. It wore a deep indigo robe. When Natsuki first saw it, it had looked "gray," but that might have been due to the angle of the dappled sunlight. As it drew closer, the color shifted to indigo, and the moss stains on the hem of the robe and the sound of footsteps treading on bark approached with a sense of reality. The person appeared slightly younger than Natsuki. Purple-tinged silver hair was cut short, and their eyes were two different colors—the left silver, the right a subtly different temperature. A thin old scar ran from the corner of the right eye. A face that never seemed to break its calm expression looked at Natsuki and Lilith in turn. Lilith called out the name with a voice mixing relief and tension. "Tio" The boy called Tio gave Lilith a short nod, then shifted his gaze to Natsuki. It was an appraising look. Not valuation or wariness, just a quiet gaze that seemed to be gathering information. "I was aware that Lilith had crossed to the modern side." His voice was calm and low. With little emotional fluctuation, but easy to hear. "However, I wasn't informed that she would bring someone with her." Natsuki adjusted his backpack. He judged it was time for introductions and opened his mouth. "I'm Natsuki. I'm a high school student and I run a café—on the other side, in modern Japan—and there's this boundary called the Curtain that connects the two, and my shop is the entrance to it, and Lilith-san wandered in first—" "Just your name." He was cut off cleanly. Natsuki froze. "...Natsuki." "Understood." Tio turned his gaze forward again. It had the atmosphere of an ending. Natsuki rewound his long introduction in his mind and considered what had been unnecessary. Probably all of it. Beside him, Lilith's mouth moved slightly. Not quite a laugh. But something relaxed in the moment Natsuki was cut off so bluntly, and he could see it at the edge of his vision. Her golden eyes softened just a little, then she looked forward again. (She was watching me.) Natsuki felt slightly wounded. *** Tio started walking. Lilith and Natsuki followed. The rhythm of the treesea changed with three people walking instead of two. Tio's footsteps showed no hesitation. He avoided the edges of moss accurately and passed through gaps between roots in a single step. It was immediately clear he knew this place well. Natsuki watched Tio's back as they walked. After a while, Tio stopped. His gaze was directed at Natsuki's backpack—or more precisely, at the ceramic cup slightly visible from the top of it. "Could I see that?" Natsuki turned back to check his backpack. A cup. One he'd brought from Café Grimoire that he used normally, brought along on a whim. "It's just a cup." "It possesses magical power of the same quality as a relic of a Curtain-keeper—one who manages the tears in the Curtain and maintains the balance between the two worlds. I'd like to confirm it." Natsuki's hands stopped. He'd never heard the term "Curtain-keeper" before. But the word touched something. A part deep in his chest that didn't yet have a name. "...No." "What is your reason?" "I don't have a reason. But I can't." Tio paused for a moment. "I'm asking for your basis." "I don't have a basis. But I can't." "Judgment based on sensation cannot substitute for logic." "That might be true, but I can't." An odd silence fell between them. Tio started to say something, then stopped. Natsuki also tried to add something, but the words wouldn't come. Neither was being emotional. The conversation simply wasn't connecting. A being who operated by logic and one who operated by sensation, each complete within their own reasoning, somehow running parallel. Lilith looked between them both and said nothing. Tio turned his gaze away from the backpack. "Understood. I'll put it on hold." "I appreciate that." "However," Tio added, "I will need you to explain your reason eventually. Even if it's based on sensation, I need to understand where it comes from." Natsuki considered those words for a moment. Not a rejection, but an offer to postpone. That was Tio's way of compromising, he understood somehow. "...Understood." Tio started walking. The footsteps of three people dissolved again into the silence of the treesea. *** The Aostem River—the main waterway running north and south through the center of the Suishin Treesea—had more water flow than expected. It was about five meters wide and knee-deep. They could cross via stepping stones, but the stones were slippery with moss. Tio crossed first. His movements were practiced as he went from stone to stone. Lilith followed next. Her small frame required a bit of a running start on each stone. When Natsuki stepped on the last stone, Tio was already waiting on the far bank. "Be careful. There's a lot of moss." "You could have mentioned that earlier." As he spoke, he stepped on the second stone and his foot slipped. A slick sensation, his center of gravity collapsing. Natsuki swung his arms to try to recover his balance—the weight of his backpack worked against him—and somehow managed to land on the next stone without falling. Water splashed, soaking into his shoes. "Are you alright?" Lilith asked. "I'm fine," Natsuki answered, stepping to the next stone. Tio said nothing. But he didn't look away. Reaching the far bank, Natsuki lifted his shoe and wrung out the water. It seeped out with a squelch. "Water got inside my shoe." "Do you have a spare?" "I don't." "...I see." A brief silence. As if he didn't know how to respond, Tio paused for a moment before looking forward again. Natsuki felt like laughing but held it in. Lilith's shoulders trembled slightly. She was laughing—not out loud, but definitely laughing. "You're laughing." "I'm not laughing." Her voice was shaking. *** A short distance after crossing the river, Tio stopped. "I'll share information." Natsuki and Lilith stood side by side before him. Tio's eyes were directed forward. Natsuki looked in that direction too. The treesea ended. More precisely, the color was different there. The ground that should have been covered in mos