"Mira-san's explanations are always hard to understand."
Yuki said honestly. Mira looked a bit troubled.
"Why?"
Aoi came to the rescue. "The mutual information is low."
"Mutual information?" Yuki asked.
"The amount of information two variables share. A measure of communication quality."
Aoi drew a diagram on the whiteboard.
"The sender's information and the receiver's understanding. Their overlap is mutual information."
Yuki began to understand. "The bigger the overlap, the better it gets through?"
"Precisely, the bigger the overlap, the more common knowledge exists."
Mira said quietly. "I see. My background different."
"Right. Mira's knowledge and Yuki's knowledge. The base is different."
Yuki wrote in the notebook. "Then how can we increase mutual information?"
"Create common context. Use concrete examples. Confirm the other's knowledge level."
Aoi gave an example.
"When Mira says 'LDPC codes,' it doesn't get through to Yuki. But 'a special method to fix errors' is understandable."
"Exactly!" Yuki was convinced.
Mira pondered. "So, I need simplify?"
"Not simplification, but translation," Aoi corrected. "Convert technical terms to common language."
Yuki asked. "But even with zero mutual information, we can still talk, right?"
"We can talk, but meaning doesn't get through. Just noise."
Aoi drew another diagram.
"Sender's entropy: H(X) Receiver's uncertainty: H(Y) Mutual information: I(X;Y) = H(X) - H(X|Y)"
"We subtract conditional entropy," Yuki understood.
"Yes. Subtract the uncertainty remaining after reception. The rest is the transmitted information."
Mira said slowly. "Communication is... reducing uncertainty together."
"Perfect expression," Aoi was impressed.
Yuki realized. "That's why close friends need few words to communicate."
"Correct. Because shared knowledge is abundant, mutual information is high."
"Conversely, with strangers, we need careful explanation."
"Exactly. To increase mutual information takes time and effort."
Mira smiled. "I will try... use more simple words."
"I'll also learn about Mira-san's background," Yuki answered.
Aoi looked at them both. "Good approach. With bidirectional effort, mutual information increases."
Yuki closed the notebook. "Getting through isn't one-way."
"Right. Both sender and receiver meet halfway. That's communication."
Mira said quietly. "Like building bridge. Both sides need work."
"Beautiful metaphor," Aoi nodded.
The three quietly left the classroom. People with different backgrounds building common understanding. It's like building a bridge.
Increasing mutual information is the effort to understand others and convey yourself.
Maybe that's what it means to get through.