Suspicious but Strong Potion Merchant

I was reincarnated as a hero in an RPG game. Named <Argo Continent Chronicles>. As the game progressed, I became the first main story protagonist, 'Paladin Cain', and saved the world. The great 'Paladin Cain' became a proper noun of the continent, but after that, on my way out of the capital as if I was running away, I met a ten-year-old child who would grow up to be the second protagonist of this game. It's been nine years since I became 'Ian', a potion merchant who settled in a small town at the southernmost part of the continent, and raised the child 'Luca' and watched him grow up. The peaceful daily life I lived in a remote place is shattered by the visit of an old colleague who came be...