Jang Cheon-Su is a first-year D-ranked student in fight class 1 at Nam-Il High. He was awarded with the "Failure at Success" award for failing in the first round of the ranking qualifications alongside Jiu Ji-Tae. He scored second to last in academics among the first years in fight classes at the Grade announcement. He is friends with O In-Taek and Cha So-Wol. He has also shown familiarity with Im Hyeong-Cheol and Choi Yeong-Jun.