Do we need to buy a travel pass?

Hi, I wonder if you can help?

We are travelling from Tokyo- Odanawa on the 8th October
Odanawa - Osaka on 9th October
Osaka - Kyoto on 12th October
Kyoto - Hiroshima on the 15th october

We think it wouldn't be cost effective to buy the pass but wondered how difficult it is to buy indivual tickets?
What is the procedure for this?

Would appreciate any help :)

Thanks