Tensei shitara Slime Datta Ken, Vol. 01

the long version

"Average, unexceptional, 37-year-old salaryman Satoru Mikami has found himself in a gooey situation. After getting killed while saving his coworkers' lives, he gets a new lease on life--just not the life he was expecting. He has been reincarnated in a fantasy world as a magic-wielding slime creature. Under his new name "Rimuru Tempest," this once-normal man will have to learn to survive in this strange, new world--and with his incredible wit, affable nature, and a few powerful allies, he'll quickly ooze his way into the hearts and minds of everyone he encounters along his journey."--