Spirit Migration

Spirit Migration (スピリット・マイグレーション) is a manga written by Hero Tennki and illustrated by Akane Kotetsu.

Plot
A spirit was floating in another world’s dungeon, missing its memories. Eventually “he” learned to possess other creatures and using the bodies of the beasts in the dungeon, made his way to the outside world. Dragging a young female knight, a pretty young lady, and even a beautiful mercenary into the mix, our protagonist begins his great adventure in this world!