Description 1. Open the Door of Time and Dive into a Great Korean History Adventure! Teacher Sul and his friends open the door of time and travel through Korean history to turn Ondal into a history genius! Through time travel, readers can vividly experience key moments of Korean history as if they were really there! 2. Build Your Knowledge with 'Teacher Sul Min-seok's More About Korean History'! Join Korea's number one Korean history teacher, Sul Min-seok, in the 'More About Korean History' section! Questions that arise while reading the comic are answered in a friendly and entertaining way, complete with visual materials. Through this section, readers can build a deep and rich understanding of Korean history. 3. Feel the Depth of Korean History Through Rich Background Knowledge! Sections like 'Ondal and Pyeonggang's Korean History Q&A' and 'Our Cultural Heritage with Robin' explore various Korean history topics related to the comic's themes in a fun and engaging way. Enjoy learning fascinating and useful Korean history facts through these special features. 4. Test Your Skills with 20 Key Korean History Questions! In addition to basic questions that check what you've learned, this book includes actual questions from the Korean History Proficiency Test. Try solving these key questions to build your application and problem-solving skills, and prepare yourself for the real exam. 5. Read Alongside Your Textbook with the 'Curriculum Connection Chart'! This book includes a curriculum connection chart based on the '2015 Revised Curriculum.' Check the chart and read Sul Min-seok's Great Korean History Adventure alongside your elementary social studies textbook. Studying social studies will become much easier and more enjoyable! Volume 27 Summary Choi Jae-hyeong: Igniting the Flame of Independence! On a spooky day, Teacher Sul and his friends visit the Independence History Memorial Hall and unexpectedly encounter a ghost. The ghost keeps repeating that a button must be delivered to Fedcha. To help the ghost, Teacher Sul and his friends travel to Primorsky Krai in Russia in search of Choi Jae-hyeong. There, they meet Choi Jae-hyeong, the leader of the village, and show him the button—but he doesn't recognize it. Determined to uncover the button's secret, they travel through time once more and happen to spot An Jung-geun. Following him, they arrive at Choi Jae-hyeong's house. But something seems off between Choi Jae-hyeong and An Jung-geun—what could have happened between them? Will Teacher Sul and his friends recover the ghost's memories and finally solve the mystery of the button?