自由研究の横に座る、他人の僕

The condensation from the barley tea had left a round mark on the table.

That day, I sat next to a fifth-grade boy—let's call him Yuta—and we looked together at the plan for his summer research project. The theme was "Investigating How Ice Melts": sugar water, salt water, and plain water. It was a simple yet genuinely scientific project, where he would freeze each in an ice cube tray and compare their melting speeds.

"Dad," Yuta said, "salt water is harder to freeze, you know. So I think it'll melt faster too."

As Yuta said this, he drew a chart in his notebook with a marker. Every time a line curved slightly, he'd correct it with an eraser. He was a meticulous child. "Oh, really? Why do you think that?" I asked back, wearing a father's face.

I was not his real father.

I received the request from Yuta's mother—let's call her Satomi-san—when Yuta was in third grade. While I can't go into detail about the divorce, Satomi-san had said, "I want to create memories for this child of doing homework with his father." Those words still resonate within me.

To create memories for him.

What Satomi-san was seeking was not a professional tutor to solve problems, nor someone to simply provide the correct answers. She wanted someone who would just sit beside him, lean in to say, "Let's see," and then, "Oh, that's good!" Someone who would laugh and say, "Almost!" when he made a mistake. Satomi-san believed that was what a father was.

I felt the same.

Summer homework, among all the requests for a rental father, carries a unique atmosphere.

Sports days and parent-teacher observation days have their "main events." Their beginnings and ends are clear, and often you just sit in the audience and applaud. But homework is different. At the living room table, time passes, slowly but surely. There's no escape. No faking it.

The child is watching.

Whether the adult next to them is truly interested in their homework. Whether they're glancing at their phone. Whether they're suppressing a yawn. They know it all. That's why I feel the most nervous during homework assignments.

Let's return to Yuta's summer research project.

After we finished writing the plan, we moved to the kitchen. We poured the three types of water into the ice cube trays Satomi-san had prepared. As Yuta measured the water with a measuring cup, he asked, "Dad, is it exactly 200 milliliters?" I leaned in from the side and replied, "Yes, perfect."

At moments like these, a deep ache resonated in my chest.

Just checking 200 milliliters together. Such a simple thing, yet this child had never had it. Not until I came.

Since it would take time to freeze, we decided to do some drills while we waited. It was "Multiplication of Decimals" in math. Yuta was good at written calculations, but sometimes got confused about where to place the decimal point.

"Dad, do I put the decimal point here?"

"What do you think?"

"...Here?"

"Count it," I said. "How many decimal places are there in the multiplier, and how many in the multiplicand?"

"Um... ah, I get it. It's here."

"That's right."

I gave him a high-five. Yuta's palm was slightly sweaty and small.

This child's hands will someday grow larger than mine. Will I still be sitting beside them then? Perhaps not. Once the assignment is complete, I will vanish. That is the nature of this work.

As a rental father involved in summer homework, I've noticed something.

For a child, homework isn't about the "content." At least, not *just* the content.

When writing a book report, it was having someone next to them, reading the same book. When their free study project failed, it was the voice that said, "Shall we try it one more time?" When all the drills were done, it was the hand that stroked their head, saying, "You did so well." What children remember when they become adults isn't the answers, but rather the atmosphere of that summer.

I believe that to be true.

That's why I can't help but wonder. Is the "atmosphere" I'm creating real?

Yuta believes I am his father. Satomi hasn't told him the truth. The more "good atmosphere" I create, the more deeply etched into this child's memory will be "a summer spent with a gentle father." Some might say that memory is painted over with lies.

Yet, the feel of that sweaty palm was real. The slightly anxious eyes when he asked, "Dad, do I put a dot here?" were real. The smile that instantly spread across his face when I said, "That's right," was undeniably real.

If the emotions are real, then it is real. I want to believe that. But at the same time, I also doubt the part of me that wants so badly to believe it.

A mother from one of my clients once told me, "Mr. Ishii, the more attached my child becomes to you, the harder it is for me to tell them the truth." I knew she was right. The better our work succeeds, the more difficult it becomes to find an exit.

Even so, I continue to sit at that table.

In the evening, the ice for our experiment had frozen solid. Yuta took three ice cube trays from the freezer and inverted each onto a plate. He lined up three timers and, with his own signal, called out, "Ready, start!"

The saltwater ice began to lose its shape the fastest.

"I knew it! Dad, my prediction was right!"

Yuta jumped for joy. I laughed too, saying, "Amazing, you're a real researcher!" I caught a glimpse of Satomi watching quietly from the kitchen entrance, out of the corner of my eye. She wasn't crying. She simply pressed her lips together and nodded silently.

I can't quite put that expression into words.

It was different from gratitude, relief, or even guilt. Perhaps it was a mixture of all those feelings. They say parents sometimes feel like crying when they see their child's smile. I don't have children, so I can only imagine. But when I saw Satomi's expression, I felt as if I understood just a little.

On the way home, walking to the station, I thought.

Next summer, will I still be sitting at that table? Yuta will be in sixth grade. His free study project might be a little more complex. The book for his report might be thicker, too. And the year after next, when Yuta moves up to junior high—the request might come to an end. Satomi might decide it, or Yuta himself might say, "It's okay, I don't really need it anymore."

And that's fine.

I don't want them to depend on me. I want them to use me as a stepping stone to build real human relationships. That's always been my thought.

But, to write honestly.

I probably won't forget that voice, "Dad, do I put a dot here?" I don't want to forget it. Whether Yuta will someday learn the truth or not, I cannot know. Nor can I know how the memories of that summer will change when he does.

However, on that day. That hot July afternoon. For that brief time when the condensation from the barley tea left round marks on the table—we were, without a doubt, father and son.

At least, that's what I believe.