Sword Art Online - Vol 1 Chapter 11

“Is this man not going to divorce me? Why does he still ask me to warm the bed every night?”

Wang Xiao was compelled to descend from the mountain by his master, with his intrinsic energy cloistered, and a lovely woman erroneously believing him to be her betrothed. In a bid to safeguard his mistakenly assigned fiancée, he resolved to remain in the school teeming with enchanting beauties. With the same intent to defend his intended, he managed to transform the currents of power within the city.

In the waves of steam and machinery, who could achieve extraordinary? In the fogs of history and darkness, who was whispering? I woke up from the realm of mysteries and opened my eyes to the world.

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?