"i dONt WaNt To GaTHer unWaNted aTTenTiOn" he says.
Then he proceeds to jump over the rooftops of the entire city, and takes out a bike the moment he's past the gates which is definitely seen and heard by guards at the gate and other people on the road, which there should be at all times of the day because it's a big city. But nah, the author didn't imagine this possibility, so therefore it is impossible for this to happen.
Of course, when he returns, noone is going to question the fact that he travelled to and from the dungeon with speeds that should be impossible with the technology their world has.
I'm going to get over this stupidness with some lolis at nhentai.