After School Labyrinth Adventurer ~ I'm now able to go back and forth between Japan and another world, and I'll work hard to level up~ is a Manga/Manhwa/Manhua in english language, ACTION series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Akira Kudo, a high school student who can freely travel back and forth between Japan and another world, Do Merta. Without any mission, he spends his time after school enjoying life in another world as he is! As an adventurer, you'll be harassed by the guild's receptionist, receive a "reward" from your magic master, and have fun with the girl you helped...! ? I hate pain! I don't care about rank! Guild requests are also troublesome! A leisurely labyrinth exploration fantasy just for after school!