MOON NOA wasn't contented with Lee Sarang's verbal explanation.
Hence, he asked the Ice Queen to bring him to the suspicious laboratory.
That was how their little group ended up in Japan.
Yes, it's an overseas trip.
Moon Noa's little group was composed of Ryu Sungbin, Lee Sarang, and Matthew. When they arrived in Japan, Jin Sooin was already there.
Apparently, Lee Sarang and Jin Sooin worked together. But Lee Sarang had to return to Korea to make a personal report to Ki Gayoon before Ki Gayoon disappeared again. Anyway, Jin Sooin stayed behind the suspicious laboratory to make sure that the evidence left there wouldn't be tampered with.
And that was how their 'little group' caused panic for the Japanese Government and the Japanese Imperial Family.
After all, Moon Noa was the first S-Class Guide in the world.
Ryu Sungbin, Lee Sarang, Matthew, and Jin Sooin were all natural S-Class Espers that belonged to the Top 5— aka South Korea's strongest Espers.
