I'm the Mysterious Leader of the Salvation Organization - Chapter 449:

Rudel Arses, the first born of one of the ‘Three Lords’ of the Courtois Kingdom, is from a corrupted family, but at 5 years old, he saw a dragon in the sky and his dark future as a villain changed. He was considered an idiot, but was that true? How would his effort to become a dragoon change the kingdom?

An ordinary (?) grandfather, Choi Chuntaek. In an effort to protect his granddaughter, he started the virtual reality game 'Arkstar.'

Then... he accidentally obtained a legendary class?

Freshly turned eighteen, John Newman, a helpless nerd, suddenly gets video game abilities granted to him. A mysterious higher power, a secret Abyss of magic beneath the surface of the normal world, mages, martial artists, eroticism, tragedy and a harem of hot girls awaits.