It's My 80th Birthday, and the System Wants Me to Save the World

From the start, he wakes up in the body of a decrepit old man, whose wealthy son is throwing him an eightieth birthday party?

Ye Tian is a little bewildered!

Luckily, the System arrives, and Ye Tian has nothing to fear.

But...

Why does the System say a global transformation is about to happen,

and that he has to save the world?

From then on, wearing a striped tank top and bean-toe shoes, and carrying a toy water gun, he goes around fighting monsters!

He fights monsters, levels up, and overcomes one challenge after another!

The ability users admire him to the utmost, while the demons and monsters tremble at the mere mention of his name.

Before long, Ye Tian has become the world's universally acknowledged strongest old grandpa!