My name’s Karina! I’m starting a new life in a new world as a different gender, but the Goddess who brought me here one-shotted the final boss in the tutorial. Now she says I can do whatever I want! So...now what?

My name is Keima Masuda, and my hobby is sleeping. But one day, I was summoned to another world where I had to save a girl from bandits in a dungeon... wait, she's the Dungeon Core?! And I'll die too if she gets destroyed?! I just wanna sleep!