Researchers at Kobe University have detected the lava dome holds almost eight cubic miles of trapped magma.
This build-up of often rock has sparked concerns Kikai is silently building up towards a roaring super-eruption.
An eruption of this scale would endanger as many as 100 million people, the researchers have gravely concluded.
]Fears are growing largely because the ancient supervolcano being responsible for one of the largest eruptions in history.
But according to Mr Tastumi’s research there is only about a one percent chance of a “catastrophic” caldera disaster within the next 100 years.
Kiki last erupted around 7,300 years ago and is believed to be the culprit behind the extinction of the Japanese Jomon civilisation.
Scientists believe the eruption released some 120 cubic miles of deadly hot magma.
The volcano sits only 50km south of Kyushu – Japan’s main island.
The lava dome itself is about 5.9 miles wide but the seabed around it has been raised upwards by some 610 metres.
Kikai’s peak can be found 30 metres beneath the Pacific ocean waves.
Mr Tatsumi said: “The lava dome is chemically different from the super-eruption, suggesting that a new magma supply system had been developed after 7,300 years ago.”
The scientists also indicated that the “post-caldera activity” is indicative of the volcano preparing for “the next super-eruption”.
However, the stark warning does not imply an eruption is imminent, but that the volcanic system has been evolving since its last eruption.
This suggests that the supervolcano has found a new source of magma.
Mr Tatsumi and his colleagues plan to further research the volcano to find more cause about what is happening beneath the surface.
So far three sonar readings of the volcano’s dome have been carried outing another is planned for next month.