Tokyo - Osaka - Koyasan -Hiroshima

Hi,

My wife and I will be in Japan for 10 days. Arriving at Narita and hoping to take the NEX to Tokyo Station. Two days later, the Shinkansen to Osaka. We are going to Koyasan for one night and then will do some day trips from Osaka --- Hiroshima, Naoshima, Himeji Castle. We will leave from Kansai.

I'm not sure whether a JR Pass makes sense or if we are better buying tickets as needed. I've been to Japan several times and have always done it that way, but it's confusing to figure out what the pass would cover and the value of savings.

Thanks so much in advance...