Travel to the Game World and Become a C-Level Guardian Beast

I traveled to the game world and became the guardian beast of a beautiful sister, but... Why am I just a C-level little **! ! ? Forget it, even if it's only C level, I still have to protect my little sister, the beast master, and take her to escape from this dangerous game world…………………………………………………… This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.