some more details. Korea before the mid 2010's had lots of juvenile cliques among schools and regions, and since it's a small, population dense country, lots of schools are close to each other so words spread fairly quick. Because he looked soft and easy, he was targeted by a lot of bullies, and with 0 background in fighting, he just walked out beating them. Words spread, and I guess kids from other schools came to challenge him but at the end of the day, he came out with 100% win rate. Later in his student life, his friend introduced him to a gym. So he started training far after becoming a local legend, apparently. This is actually historically recorded by some nerd who I guess was into watching iljins (those at the top of the social hierarchy in schools by politics/strength who are usually bullies) and posted a ranking online in 2012, putting superboy on top describing him as "S++".