time travel is currently deemed as fiction only, at least to me.

As einstein stated in his theory of special relativity, there is no object can travel faster than the speed of light.

Most theories suggest that you can do time travelling when you can exceed the speed of light. But if you cannot exceed the speed of light, then any theory beyond it will be falsified automatically.

A speed near to speed of light will have the effect of time dilation but not time travelling.

Perhaps we can have some new theory in the future that suggest some new models of space time. Let's wait and see.

what you are saying doesn't have anything to do with travelling faster than speed of light at all.

Do realise that space-time in general relativity is not as easy as you thought. I don't know who is hiro nakamura and a google seems to be a drama character?

You do realise that real physics and Science fiction are totally 2 different thing?

time dilation has nothing to do with time travelling at all.

The twin paradox which is based on time dilation is just an effect observed from special relativity.

Those who studied special relativity should be able to understand twin paradox easily.

For those who don't, it's good for you to learn some.

Actually, anyone who travel on bike or car or plane would live a longer life compare to your friend standing on earth (the initial frame). However, the effect is too little (perhaps the range of less than few nano seconds) thus having no impact at all.

However, a number like 0.8c will have such effect by then.

Those who are interested you can study length contraction as well.

To TS, what you mention is wormhole, another theoretical proposal which still haven't been proven until today. However, i do believe wormhole exists as in GR but doesn't promote time travelling. GR is not really my field so my statement is not really correct. It is just a believe rather than a physics research.