18+ Ossan wa Isekai de Omoi wo Togeru

An old man wrongly accused of groping ends up, before he knows it, in a mysterious temple with a suspicious goddess, together with a high school girl, Mizuki. The goddess Rakshel mediates the two as they continue bickering and gives them a royal order to defeat the Demon King. After receiving only three cheat-type special skills from the goddess, the old man is transported to another world along with Mizuki.

It's a medieval Europe–like world where the concept of levels exists. And on top of that... the Demon King they're supposed to defeat was already slain 100 years ago.

To begin with, with the old man's abilities, even taking down small fry like goblins is a struggle. To survive in a harsher-than-expected other world, he decides to buy a slave and form a party. That's where he meets Fam, a beautiful dog-eared girl. Together with Fam, the old man steadily works as an adventurer, tackling dungeons and quests one step at a time...

This other world isn't so easy!

(Source: Magazine House, translated)