Narita to Kansai - Is a JR pass needed?

Hi,

I'm debating if I should get a JR pass or not. I'm flying into Narita Airport on October 16th and flying out of Osaka on October 25th. I'm planning on spending the first 3 nights in Tokyo (in Shibuya area), then spending the next 3 nights in Kyoto (near the Kyoto Station) and then 3 nights in Osaka (in Namba area). I know if I was going round trip across Japan, the JR Pass would definitely be worth it but I'm not so sure about just one direction.

I remember the last time I was in Tokyo I mainly used the Metro lines and not JR lines but I definitely used JR more in the Osaka and Kyoto areas so maybe a 7 day pass would work best and just activate the pass the last 7 days of the trip. I was looking at ticket prices for the bullet train from Tokyo Station to Kyoto station and with daily travel and the JR line from Osaka to Kansai airport, to determine if it's more than a 7 day JR pass. But I am still undecided and decided it might be best to see another opinion.

Any advice or suggestions on this would be greatly appreciated. Thanks in advance.