Why address '367f4YW...' pay to itself?

While reusing addresses is not recommended for various reasons (privacy, security, etc), there is nothing stopping someone from doing so. If you'd like to send the change of a transaction to the same address you used an input from, you can do so.

is it available to guess a relationship between '367f4YW...' and '15ozxv...'?

In many cases, if there are multiple inputs, you could assume that they are all controlled by the same wallet.

However, that is not always true. For example, P2EP transactions are looking to break this assumption, so that it is harder to guess at the nature of each blockchain transaction (ownership of inputs, outputs, etc).

For bitcoin to work best, fungibility is important. Making transaction inputs/outputs harder to decode is an important part of maintaining fungibility!