So Lostbelt 5 in Olympus Chapter 3 has this feat where Musashi blocks a lightspeed attack which Holmes predicted. Found two translations both by fallacies, though the first one is a summary of sort:
Apparently the Dioscuri twins have the authority to move at "superluminous" speed, but using it fully will destroy their Saint Graph.
In Chapter 17 Castor decides to move FTL in order to take Ritsuka as hostage, but coughs up blood as a result:
This can potentially be the most powerful evidence so far for relativistic. It is wiser to wait for the full translation when the NA release arrives, but some questions that needs to be addressed first:
Did Musashi or Holmes get a dose of nanomachines like other characters?
How does Holmes informs Musashi of his predictions?
What does Holmes predictions entail, is it a vague 'an attack is coming' or is it something more precise?
Does this constitute aim dodging?
As a bonus there is a statement that both Musashi and Billy the Kid are faster than lightning: