What's it about?
Setting: Mediaeval stylefantasy land
When he tries to save a girl he thinks is about to be hit by a truck, Kazuma Sato ends up in limbo, where goddess Aqua gives him a choice: move on to heaven, be reincarnated on Earth or go in his current body with his memories and abilities intact to an RPG style fantasy land. That land is in crisis, and Kazuma could be a hero in their fight against the Devil King.
When told he can take one thing with him, maybe a skill or a weapon, Kazuma chooses Aqua herself... only to regret it as soon as they reach the new world. Now he is stuck with an devastated goddess with below average intelligence and no combat skills, who can't leave until the Devil King is defeated.
How's the fanservice content?
First fanservice: 1 minute 29 seconds in, when we meet Aqua. Well, Aqua's butt. I think whoever draw this was expressing their unhappiness with their job through the medium of weird proportions.