Japanese Princess Mako's fiance-to-be lists playing the violin as one of his hobbies, and has one person particularly delighted at his continued passion for the instrument -- his childhood violin teacher.

"He was a student who diligently worked hard" at the violin, Junko Yamauchi, 66, said of Kei Komuro, who attended her violin school in Yokohama, southwest of Tokyo, from age 3 to the upper years of elementary school.

Komuro, a 25-year-old paralegal, was thrust into the limelight after news broke late Tuesday about his planned engagement with Princess Mako, also 25, the eldest grandchild of Emperor Akihito.

Yamauchi recounted that when she put out fliers for violin students after moving to Yokohama due to her husband's job transfer, Komuro's mother was the first to make contact.

She recalled that Komuro worked hard to learn the basics of the violin, saying, "When he was very little, he would continue practicing and holding on to his violin while half-asleep."

Even when the boy moved to Tokyo to attend a private elementary school, he and his mother would come to her class once a week. His efforts eventually paid off and his skills steadily improved.

But Komuro stopped his lessons with Yamauchi around 15 years ago when his father suddenly died. Yamauchi said, "I heard that his mother took on different jobs and I can imagine (how they) went through a lot of hardships."

(Junko Yamauchi)

She met the mother, who returned to Yokohama, several times after that and was updated about her former student's life, including the fact that he and the princess were attending the same university.

"I was very happy when I learned that Kei went to an international school and continued with the violin," she said.

Yamauchi said she met Komuro around a month ago for the first time after more than 10 years, and that he was the one who approached her. She remembered how proud she felt to see how the little boy had turned into a fine young man.

Yamauchi said it would now be hard to see him, but that she has a simple wish for her former student. "Someday, I would like to hear him play with members of the imperial family."