Young-Chul was busy staring at Kyung-Soo sitting in a corner staring at his tablet. For days now, he didn't talk to anyone, he was not eating with them, he was not spending time with them, they were not even aware if he was in the house.
Young-Chul was looking at history repeating itself. He too did the same when he was struggling. He would shut himself in his room and not talk to anyone or eat with anyone. He loved his privacy which now he understood was his loneliness. And he was watching Kyung-Soo go right down that very path.
He tried talking to Kyung-Soo multiple times, but he would just shut himself in his room or walk out of the house. Young-Chul kept thinking and thinking about the change in his behaviour and now he had his suspicions.