The book commemorates the retirement of Kang Yoonsung, a graphic designer and university professor. Since ancient times, there has been a custom in Korea to make rainbow rice cakes on auspicious occasions such as 100 days, 1st birthday, marriage, and 60th birthday. He hoped that retirement would be a feast day, not a sad day, so the concept of the book became rainbow rice cake. The book was composed of letters from 60 colleagues and disciples from Korea, China and Japan, and design work by Kang Yoonsung. The book was designed using colored paper to express the rainbow rice cake.

Kim sunghoon is a graphic designer based in seoul, south korea. Starting with graphic design based on typography, he is a graphic designer who is interested in using various visual languages such as image and digital as a means of communication and is working on a number of projects. He is working on a variety of projects with different personalities, creating each communication tool that fits the project as a result of the design. By doing so, the company is expanding its scope to graphic design, such as public design, space design, signage design, exhibition design, information design, brand design, digital design.

Korea's leading graphic designer and professor at Kyonggi University. Under the theme of Korean traditional culture, posters and books have been designed, and C.I. work has been carried out by companies such as Kyonggi University and the Korea Economic Daily.