The Akatsuki was deployed by Interpol to search for the wreckage of Mechagodzilla in the waters off Okinawa. While the submarine searched for Mechagodzilla, it was suddenly attacked by the monster Titanosaurus. The sub tried to surface, but Titanosaurus did as well and dove onto it, dragging it back underwater. Titanosaurus then grabbed the Akatsuki in his hands and crushed it until it exploded.
Later, Interpol constructed a new submarine, the Akatsuki II, to search for Titanosaurus. This submarine was equipped with radar to make it easier to detect Titanosaurus. When Titanosaurus attacked the sub, it was unable to escape the creature. One of the crew members activated the sub's sonic wave oscillator in desperation, which surprisingly caused Titanosaurus to writhe in pain and retreat, saving the Akatsuki II. The sub's sonic wave oscillator was later weaponized and mounted on a helicopter as the J.S.D.F.'s best hope of defeating Titanosaurus.