In the Tiga universe, on Earth.
Although the threat of Gatanothor was gone, GUTS still had to deal with Kaiju appearing from time to time. Even though Daigo could no longer transform into Tiga, fortunately, there was still Rei, transformed by Masaki Keigo, along with two Kaiju helpers, Gaby and Silbagon. Moreover, the current technological level of GUTS was far beyond their previous minor tinkering.
As for Darram and Hudra, Iruma Megumi stated that they could do as they pleased.
Chapter 234