I doubt Ijin knows all loopholes and his age gives options to twist his testimony.
Ijin has 10 years of "experience" as a mercenary. It is clear that he knows how to at least omit information, perhaps dissimulate. We did not see him "lying" (or I don't remember). The feeling is that even other mercenaries fear or respect him because he shows this.
Being a politician means a lot of money and connections. You can't get both as a good person.
Not that. Remember that "a politician is a mirror of those who elect him". Good politicians know that at the same time they have to reconcile the desires of their group, which they protect and lead, as well as negotiate with outside groups - that is what real politics is. But capitalism is the sale of this power. It is not for nothing that I mentioned corrupt politicians. They do not care about the population, just like the congressman who ran over and ran from the scene of the accident. Think about it.
(By the way: South Korea has a "complex hierarchy" issue, which is dealt with in some other series, but not exactly and completely in "Teenage Mercenary". This "complex hierarchy" generates a lot of corruption, as it ends up encouraging nepotism and conflicts of interest.)