That's actually pretty much it. Kid is told he has 100 soulmates and let the fun begin. Definitely ecchi but nowhere as lewd as Immoral Guild.

Noteable differences to most harem anime are:

1. The protagonist does actually start dating every member of the harem instead of keeping the status vague.
2. The protagonist is dedicated to his girlfrieds to the point that viewer want to cheer him on.
3. The girlfriends have quirks that seem flat when written down but are well executed. Especially in later episodes where crazy plot lines are introduced.
4. After the initial episodes it becomes an absurdist comedy with well done references to other media.(Misson Impossible, Resident evil, Pokemon). Like a plot hook might call an alien invasion and it gets resolved by having the alien leader being one of the soulmates of the protagonist.