Vibration Warhead Torpedo is the newest generation of human-made torpedoes and a weapon that can be potentially-dangerous even to the "Fleet of Fog" vessels. The only field test done against a torpedo boat has been successful.
Unfortunately, Japan, where this torpedo has been designed, doesn't have resources to produce it en masse. Out of the five prototypes created, only one still exists at the moment.
Vibration Warhead TorpedoEdit
The Vibration Warhead Torpedo was the result of analyzing the Corrosive Warhead Torpedo possessed by the Fog. However, reproduction was impossible due to the lack of knowledge of Thanatonium. Therefore, the Vibration Warhead Torpedo was born.The basic idea behind the Vibration Warhead Torpedo is that any physical existence, be it more conventional materials used by humans or the nanomaterials of the "Fleet of Fog", will crumble when it vibrates at its own fundamental frequency. The warhead of this torpedo attaches itself to the hull of the target and, after analyzing it, starts vibrating at this fundamental frequency, leading to the resonance disaster. This is due to the warhead containing Somnium, creating an effect much like that of a Corrosive Warhead Torpedo. The only weak point that prevents this warhead from being truly effective against the "Fleet of Fog" is the fact that it still needs to get inside the Klein field deployed by the vessel's Wave-Force armor: the warhead is useless if it cannot come in contact with its target. Although theoretically it is still achievable if the ship's Klein field has almost reaches saturation point and a Vibration Warhead Torpedo is launched afterwards, the torpedo itself generates an energy field with the ability to penetrate a Klein field (although probably a weak one).
The idea to create such torpedo has existed for a long time. However, because torpedoes need to be small, and their payload even smaller, while still reliable and effective, such weapon could not be developed by the humans at the time. In order to make the creation of this torpedo possible within the reasonable time, the genetically-modified humans with the potential to do what normal engineers couldn't were created. The creation of the Vibration Warhead Torpedo was the mission of the seventh so-called Design Child, Makie Osakabe, and she had successfully completed this mission.
Still, the torpedo was not something that Japan could mass-produce and only five prototypes were created. At least one of them was used for the field test, where a "Fleet of Fog" torpedo boat was successfully destroyed with a one hit. With the proof of the weapon's effectiveness, the agreement with USA was made - America was among the countries that still had the resources to produce the Vibration Warhead Torpedoes en masse and it was the only such country not involved in any human-vs-human wars. "Fleet of Fog", however, could also see the potential danger such torpedo presented, and so they did their best to prevent USA from getting the blueprints or the prototype.That included jamming satellite transmissions and shooting down an SSTO with the torpedo prototype on-board (the very same SSTO I-401 and Gunzou Chiahaya had protected from the attack of light cruiser Nagara).
With no other options left, the assistant secretary to Japanese Military Command of Ministry of Defense Ryuujirou Kamikage decided to make a bold movement and hire I-401 and Gunzou Chihaya to make the trans-Pacific delivery. This decision had some opposition among the higher-ups of the Japanese government, not in the least because Gunzou Chihaya was considered a traitor at that time because of being in possession of a "Fleet of Fog" submarine, the I-401. However, this opposition had to accept their defeat eventually.