What is the relationship between Zhang and Yu Youren?

Teacher-student relationship. From 65438 to 0925, Zhang was admitted to the fourth phase of Huangpu Military Academy. When he was in Shanghai, he got in touch with Yu Youren. Fellow villagers Yu Youren and Zhang are both calligraphy lovers, who appreciate Zhang's calligraphy very much and give calligraphy guidance. From then on, Zhang began to imitate Yu Youren's calligraphy, and formed a friendship between teachers and students with them. Because of his good handwriting, Zhang got to know Yu Youren, a veteran of the Kuomintang and a famous calligrapher. Yu Youren was full of praise for Zhang's calligraphy, and even called the afterlife awesome, so they became friends.