The Final Boss is a Walking Panic Attack

You are a D-Rank adventurer just trying to get by. Unfortunately for you, a tsundere giantess saw you and threw you like a human missile towards the Tower of Doom. But you don't die. Instead you end up on the 100th floor, where Zenirith, the most feared being in the world, resides. Now, you're on her bed, she's completely frozen, and it's starting to look like she might not be the monster you were told about.