Finding My Gundam (2013)

Hyun-dong is a hikikomori. He lives off of the joy of assembling and displaying Gundams in his only space, his home. Then one day, he makes a big decision to go out to buy a Gundam plastic model that a delivery man left next to his door. At that moment, the front door slams shut. He is trapped in an unfamiliar world, he can't remember the password and he decides to go on a long journey to find the key house.