Alcohol can have vast reactions for each person.
Some can handle it and drink a russian Don under the table, others get shitfaced after a small amount as seen with JJ.
Hell, there is even people with medical conditions that can have other reactions, as is the case with some korean people that genetically cannot drink alcohol due to risk of death.
Body build DOES play a big role. Him being heavy doesn't matter as much as his body being lean and other factors that make his system work differently.
There's also something to all this as it's a VERY commonly used trope in stories in asia, so you'll likely find people getting drunk more easily over there than with other countries. Else the cliche would be common in western fiction as well, which it isn't. Likely because our relationship to alcohol is a bit different and rooted in our systems even. XD
there’s no way that massive guy got drunk from 1 sip of soju lmao common sense doc please