Mothra is a tame Class 5 Kaiju encountered in Tokyo with 2 other now tame Kaiju.
Mothra was one of 3 Kaiju who attacked Tokyo at the same time. The others being Rodan and Godzilla. All 3 were detained in infancy so taming was possible. Mothra was named the Glorious Queen by it's captors. Mothra was described as gentle and shy compared to it's more rambunctious "brothers".