Divine Glitch: I Regressed With Endgame Knowledge - Chapter 3: First In

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?

He was the continent’s strongest and most revered alchemist, Ye Zifeng. He was under one person and above millions. However, due to an unpredictable event, he had died. After his rebirth, he had become the supertrash of the Ye family and suffered disgrace. To make matters worse, he had an argument with his fiancé that led to the break off of his engagement. In this second life, he will work to change his own destiny. He vows to return to the peak of the world, trample on those who laughed at him and rewrite his legacy!

- Description from Novelupdates

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?

My brother* and I, from elementary school to university, had grown up together. We didn’t just get into the same degree, we’re also sharing the same dormitory room.