A bomb was dropped right in Misaki's face now.

  "W-When did I ever agree to that..."

  She remembered saying something silly like that to Shirogane, but it was just a joke!

  I mean, who could have thought that she would die and suddenly reincarnate into the past as her little sister!?

  "Hmm, are you pretending to forget, Senpai? With that super memory of yours? I’m not sure."

  "Besides, this is the Senpai I know very well."

  Shirogane kept teasing her with a grin, and Misaki couldn’t take it anymore and finally shouted at him.

  "Geez! Fine, I did say it! But I only said it as a joke! Who would have thought something like this would actually happen!"

  Misaki’s embarrassed outburst and her flurry of light punches were enough to make Shirogane ugh.

  Seeing him like this made her feel better because, in the past, she had a much harder time expressing herself in many situations.

  "Okay, okay, alright. Stop hitting me. I was just saying it to lighten the mood. I didn’t mean to hold you to it... Well, it’s a shame it wasn’t a promise from Senpai herself."

  "...You’ve gotten really good at teasing, huh."

  Misaki sighed, finally calming down after realizing it was all just a joke.

  "But, Senpai, you have to pay for those words you said by kissing my cheek."

  Shirogane added, pointing to his smooth cheek.

  "...That’s also a joke, right?"

  "No, this time I’m serious."

  "I don’t want to!"

  After a few quick punches, Misaki was too tired to move and could only pant while looking at Shirogane’s head, which now had a few bumps.

  "...Ahem, let’s move on to a more serious topic."

  Pretending to ignore the pain from the bumps on his head, Shirogane’s expression turned serious.

  "Do you still have the clover I gave you before?"

  "You mean the one you gave me at school that time? It’s here."

  Misaki pulled out a transparent gss-like object with intricate carvings around it, inside of which was a four-leaf clover. This was the item Shirogane had given her earlier when he skipped school and came to see her. That was all Misaki knew. She was still wondering why Shirogane had seriously told her to keep it and carry it everywhere as if her life depended on it.

  "As I said back then, please keep it and carry it with you wherever you go. Your life depends on that clover."

  Shirogane said seriously.

  "...You’re joking, right?"

  "No, I’m serious."

  Shirogane’s tone grew heavier as he repeated it, making Misaki realize the situation was far worse than she thought. But she still didn’t know why or what the reason behind it was.

  "Why? What’s going on?"

  "Do you know what causality is?"

  What’s this now? Why is he bringing this up?

  "Causality is the w of cause and effect. Everything that happens in this world has a cause and origin. At the very least, you understand that much, right?"

  "Yeah... I at least understand the general idea."

  "Good. It’ll be easier for me to expin from here. Your birth had a cause, and my birth had a cause. We both know that, right?"

  "Yeah."

  "The w of causality still applies normally to that. But what about your actions when you intervened in that murder incident back then? From the perspective of causality, that can’t be considered normal in terms of cause and effect because you shouldn’t have known when, why, who, or how that incident happened. That already viotes causality."

  "Wait, wait. If that’s the case, wouldn’t every action and behavior I’ve taken so far also viote causality itself since I’ve been slowly changing the future around me?"

  What about Kazuto, who originally didn’t py basketball and was a gloomy person, but now he’s the opposite? The new friends she’s made? The behavioral shifts of those who interact with her—wouldn’t all that also count as a viotion of causality if that’s the case?

  Fortunately, Shirogane gave a positive answer by shaking his head.

  "No. You have clear connections with the people and environment around you, so that doesn’t count as a viotion of causality. The problem now is that you intervened in a murder incident that was supposed to happen, and you did so without any connection. You didn’t know the perpetrator, the victim, or their family, so the w of causality will calcute this."

  "Then, what actually happens to someone who viotes causality?"

  Misaki asked.

  "Misfortune."

  Shirogane answered briefly.

  Then he added.

  "That misfortune could be small or big, I don’t know. But you should be careful with causality. Don’t try to underestimate it."

  Shirogane warned seriously, as if he had experienced it himself.

  But Shirogane’s serious face quickly turned into a smile as he pointed to the clover.

  "That’s why I gave you the four-leaf clover. With it, you’ll receive the smallest misfortune that isn’t too dangerous. Well, at least you’ll slip somewhere ter."

  He said casually.

  "Geez, if it’s like that, why did you have to make me worry about all this, you dummy."

  Misaki pouted. She had been made to think about something serious, but it turned out to be nothing at all.

  "Haha, it was just to make sure you’re careful with that clover. If it’s lost, make sure to stay in one pce and call me."

  "So that’s why you’ve been coming to my house and sometimes touching me—to give me some kind of luck?"

  "Well, you can think of it that way."

  Shirogane said while scratching the back of his head. He hadn’t expected Misaki to figure that out, so he felt a little embarrassed when she mentioned it.

  "I see..."

  Shirogane... had been watching over her quietly all this time. He had been doing this and that behind the scenes so Misaki wouldn’t have to worry. All this time, he had been trying to protect her in his own way.

  But what about him?

  "And what about you?"

  Misaki asked, looking into his eyes.

  "About what?"

  Shirogane asked back, tilting his head.

  Misaki could tell he was pretending to be clueless, which made her annoyed.

  "Obviously about this causality thing. You’ve changed the future in many pces without any connection. I can tell. So doesn’t that mean you’re in even greater danger?"

  "Haha, my very existence is like a viotion of causality. And... I’ll pay for it ter."

  Shirogane answered with a ugh.

  That ugh... it felt like he was comforting himself. It was too lonely.

  "Here."

  Misaki said, holding out the clover to him.

  But Shirogane refused, saying, "The clover isn’t enough to withstand the punishment from causality. But you can rest easy, it’ll still be a long time before I have to face that. Keep it for yourself; you need it more now."

  "...How severe will the punishment be for you?"

  "..."

  This time, Shirogane didn’t answer and just gave her his best smile... A smile that looked so gloomy to Misaki.

  "I... I’ll help you someday, I promise! Just remember that!"

  Misaki excimed, startling Shirogane with how sudden it was. But he soon smiled again, thanking her deep in his heart because he didn’t feel so alone when he heard those words.

  "Say that when you’re at least as strong as me or stronger."

  He replied while ruffling Misaki’s hair.

  "S-Stop! Argh, why does everyone like to mess with my hair!!"

  ___

  "See you ter, Senpai."

  "Mhm. Come over to my house more often. I’ll treat you a cake!"

  After their long conversation, they finally parted ways. Besides, Misaki had gone out under the pretext of buying something. She was afraid Kazuto would come looking for her, worried like he had done before.

  Shirogane, still sitting on the park bench, just watched her leave with a faint smile. As he always did.

  "I’m starting to wonder if I should tell her that Kazuto is her sister."

  He muttered after Misaki disappeared from view.

  "Sigh, I’ll just let fate decide."

  He said while looking up at the sky, as if someone was watching him from above.

  "You see it right, giving me such a hard task while enjoying yourself up there. I want to punch you at least once."

  He compined as he stood up.

  Looking down, he saw a pebble in front of his feet and without thinking he kicked it.

  "The future has changed once again."

  He walked away with those words.

  Meanwhile, the pebble he kicked kept rolling downhill. A child who happened to see the pebble stopped in front of it and also kicked it, sending it rolling somewhere until it reached a busy asphalt road. The pebble continued to roll between spinning tires until it finally escaped onto the sidewalk. A cyclist riding on the sidewalk accidentally hit the pebble because he didn’t see it, causing him to lose bance and fall. An old woman who was about to cross the street when the pedestrian light turned green saw the incident and came to help him. But before that, a speeding car passed through the intersection the old woman was about to cross, startling her and making her freeze. Meanwhile, the car stopped after crashing into a utility pole. The incident was so shocking to everyone there that, without anyone realizing, just from a pebble kicked by someone and through a series of random, interconnected events, two lives were saved.

  The future had changed once again, as Shirogane had said.

  And the person who changed the future just kept walking without knowing the result of his actions.

  "Hmm, did I do something?"

  He asked as he looked back.

  ---

  Meanwhile, Misaki.

  "I’m home."

  "Welcome ba-"

  As soon as she got home, she went straight to Kazuto, who was still watching TV, and hugged him.

  "...Did something happen?"

  Kazuto asked, a little surprised by Misaki’s sudden behavior. He didn’t see any injuries or anything unusual about her, so he was a bit confused about how to handle it.

  "Nothing. I just want to stay like this for a while."

  Misaki answered. She had heard too much today, and it had drained her mentally because she was now also tangled up in this causality thing or whatever it was.

  "Let me stay like this for a while."

  "...Anything for my little sister."