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Summery: (from Webtoon Live)
He awakens. For 820 years he has slumbered with no knowledge of mankind's advancements and scientific successes.
The land which he once knew has become an unfamiliar place with new technologies, attitudes, and lifestyles.

Cadis Etrama Di Raizel (aka Rai), while seeking to familiarize himself with this era, somehow locates a loyal servant of his,
Frankenstein, who is currently the principal of a South Korean high school. Rai decides that this high school would be the perfect
place to help him learn about the new world.

He enrolls, and suddenly becomes the friend of Shinwoo, an immature teenager who is also a master martial artist.
But this new world is no safer than the old, and the dignified, bewildered, technologically illiterate Rai finds himself caught up
in adventures both ridiculous and dangerous.

This Webtoon Manhwa started on the 30th December of 2007 and is still publishing.