Exactly what the title says. More often that not I see others summarize, if not outright dismiss, Shorinji Kempo as a "Japanese version of Shaolin Kung Fu," although I know for a fact that SK has more than one ancestor art.

I'm aware that Doshin So was taught Jujutsu by his legal guardian in his younger years, and it's also said that Mr. So was a Karateka (Although to my knowledge, which school of Karate he hailed from was never specified upon).

I'm sure that Kaiso has trained under many fighting styles and incorporated elements from those into SK over the years, but unfortunately there is hardly any information available in regards to that matter (at least in English).