To elaborate on Dershock's answer, ziki's "Eye of Adventure" makes for a decent match.
I also remember that main protagonist was taught swordsmanship by his grandpa. (note, 'white weapon' is "a common Arabic term for any non-firearm type weapon used for self-defense or killing including swords, daggers, sticks, and batons among others.")
Most of his free time, Arthur spent on training. His grandfather taught him many things, hand to hand combat, white weapon combat and ways to be strong. Arthur thought that it may help him in repeating his debt that he always felt he had.
At the start of the novel they were in a tutorial town where their actions would determinate classes that they could choose later.
Everyone get their classes assigned by system depending on your first month of play. There are also special items or circumstances that let you change the class later on but you probably won’t ever see it as it’s extremely rare. Don’t count on that.
And as per your subject, one of his classes is "Twilight Swordsman".