Hi there!
In most cases I think that it would be best to buy normal tickets as you travel. A one way Osaka - Nagoya is ¥ 6,580 and a one way Nagoya - Kyoto ¥ 5,840. Visiting both places once would not add up to enough for a JR Pass to pay off. However there are some scenarios where a JR Pass would be helpful. For instance, you could stay at your friends place every night and take a Shinkansen from Nagoya to either Osaka/Kyoto each day. This would allow you to save money on accommodations and you could use the JR Pass to cover all your costs. Kyoto for instance is only 36 Minutes away from Nagoya by Shinkansen.
If you don't have a JR Pass, then I would recommend staying in either Osaka or Kyoto on the 3rd of April as the price for a one way ticket Osaka - Kyoto is just 540yen, you could save a lost of money by not returning to Nagoya for a night.
Hope this helps!
Daniel