Masato Jin is an eccentric genius engineer who finds minor flaws to be more interesting than perfection. Though working in another block during the incident 13 years ago, Masato ended up in subspace regardless when his fellow researchers sacrificed themselves to trap Messiah 13 years ago. Trapped in Hyper Space, Masato created Beet J. Stag to aid him when he sends an avatar of himself into reality. Using the avatar to interact with the primary Go-Busters, Masato gained the ability to transform into the Beet Buster.
Beet J. Stag (ビート・J・スタッグ Bīto Jei Sutaggu)/Stag Buster (スタッグバスター Sutaggu Basutā)
Beet J. Stag is Masato's Buddyloid that takes the form of a Japanese rhinoceros beetle/stag beetle-type android, his middle name is a short for both "Justice" and "Jueki" (樹液?, tree sap). Created in Hyper Space by Masato, J was sent to reality by stowing in a Vaglass Megazord that Enter transported. Like Masato, J is an egotist who likes appearing cool, though he has a habit of always standing in the way of Masato, which greatly annoys his creator and partner. Unlike other Buddyloids, J is fully battle-ready and he is outfitted with a Marker System that allows him to recreate Masato's avatar if destroyed. He is Jin's partner both in and out of combat, with the ability to transform into Stag Buster to actively fight alongside Beet Buster, as well as summoning their Buster Machines.
BC-04 Beetle (BC-04ビートル Bī Shī Zero Fō Bītoru): The BC-04 Beetle is an experimental Buster Machine that was being developed to aid the Go-Busters. However, Enter manages to steal its blueprints before it can be constructed, so it can be built within sub-space by Messiah's engineers. However, Masato is able to build the BC-04 Beetle within sub-space and uses it as his Buster Machine while modifying it to siphon Enetron from its target. The BC-04 Beetle has a crane Buster Vehicle mode and a Japanese rhinoceros beetle Buster Animal form. The "BC" in its name stands for "Beetle Crane".
SJ-05 Stag Beetle (SJ-05スタッグビートル Esu Jei Zero Faibu Sutaggu Bītoru): The SJ-05 Stag Beetle is a Buster Machine independently built by Masato and it serves as Stag Buster's Buster Machine. Its Buster Vehicle mode is that of a jet aircraft that normally rests on the BC-04 until activated and assumes its stag beetle Buster Animal mode where it can siphon Enetron from an opponent. The "SJ" in its name stands for "Stag Jet".