Decision is an event from Natsuki Chronicles.
It takes place right after Natsuki was shot down in the space elevator battle from Ginga Force.
While the Enforcer "Hound 1" headed to space to reunite with their former enemies and engage the RDF's forces, it is revealed that Natsuki survived her fall from the space elevator. Despite being damaged, her Garm was able to make an emergency landing at the bottom of the elevator and no one is coming to rescue her.
Realizing the situation was too good to be true, she deduces that the true Specia took control of Garm when she blacked out. Believing on Margarette's words, she decides to split off the RDF.
In Stage 8, Natsuki discovers that the RDF will go after "Hound 1" once they leave the space elevator. With Specia being swapped out, all of Seven Tier is on high alert. Thus, she decides to help her friends by destroying the RDF Orbital Base. Realizing she can use one of the spare Dominators in the RDF hangar near the elevator, Natsuki puts her plan in motion.