① Textbook for Class 4 Hazardous Materials Handler (Otoshu) aiming for quick success using manga and mnemonics. ② U-Can's Class 4 Hazardous Materials Handler 4th Edition Question & Answer & Summary of Key Points I studied with these two books for about a month last year and passed the Class 4 license on the first try! I recommend it to those who want to obtain a license through short-term intensive study, so please consider it. Thank you for viewing.